diff --git a/InterSpec/DetectionLimitSimple.h b/InterSpec/DetectionLimitSimple.h
index f0500d35..a6802a20 100644
--- a/InterSpec/DetectionLimitSimple.h
+++ b/InterSpec/DetectionLimitSimple.h
@@ -156,6 +156,8 @@ class DetectionLimitSimple : public Wt::WContainerWidget
   
   void handleFitFwhmRequested();
   
+  void handleSelectDetectorRequested();
+  
   void handleSpectrumChanged();
   
   void handleUserChangedRoi();
@@ -250,6 +252,7 @@ class DetectionLimitSimple : public Wt::WContainerWidget
   NativeFloatSpinBox *m_fwhm;
   Wt::WText *m_fwhmSuggestTxt;
   Wt::WPushButton *m_addFwhmBtn;
+  Wt::WPushButton *m_selectDetectorBtn;
   
   Wt::WLabel *m_continuumPriorLabel;
   Wt::WComboBox *m_continuumPrior;
diff --git a/InterSpec_resources/app_text/DetectionLimitSimple.xml b/InterSpec_resources/app_text/DetectionLimitSimple.xml
index 27bbab3b..bcca056e 100644
--- a/InterSpec_resources/app_text/DetectionLimitSimple.xml
+++ b/InterSpec_resources/app_text/DetectionLimitSimple.xml
@@ -3,6 +3,7 @@
   <!-- dls- is short for DetectionLimitSimple
   -->
   <message id="dls-fit-fwhm-btn">Fit FWHM...</message>
+  <message id="dls-select-drf-btn">Select detector...</message>
   <message id="dls-further-details-link">further details...</message>
   <message id="dls-conf-level-label">Confidence Level:</message>
   <message id="dls-roi-lower-label">ROI Lower:</message>
@@ -57,7 +58,21 @@
   <message id="dls-Limit">Limit</message>
   <message id="dls-continuum-area">Cont. Area</message>
   <message id="dls-DOF" remark="Degrees of freedom abbreviation">DOF</message>
-  <message id="dls-"></message>
+  <message id="dls-Upper">Upper</message>
+  <message id="dls-Lower">Lower</message>
+  <message id="dls-Best">Best</message>
+  <message id="dls-ROI-range-label">ROI Range (keV)</message>
+  <message id="dls-ROI-Channels-label">ROI Channels</message>
+  <message id="dls-ROI-Width">ROI Width</message>
+  <message id="dls-det-intrinsic-eff">Det. Intrinsic Eff.</message>
+  <message id="dls-solid-angle-frac">Solid angle frac.</message>
+  <message id="dls-air-trans">Air transmission</message>
+  <message id="dls-gamma-intensity">Gamma Intensity</message>
+  <message id="dls-err-more-info-title">Error computing limit...</message>
+  <message id="dls-err-more-info-content">Error computing limit information: {1}</message>
+  <message id="dls-err-select-det">Please select a detector efficiency function.</message>
+  <message id="dls-err-neg-distance">Distance can't be negative.</message>
+  <message id="dls-err-no-fwhm-info">Detector efficiency function does not have FWHM info - please fit for FWHM, or change detector.</message>
   <message id="dls-"></message>
   <message id="dls-"></message>
   <message id="dls-"></message>
diff --git a/src/DetectionLimitSimple.cpp b/src/DetectionLimitSimple.cpp
index fd8881fb..b161276f 100644
--- a/src/DetectionLimitSimple.cpp
+++ b/src/DetectionLimitSimple.cpp
@@ -210,6 +210,7 @@ DetectionLimitSimple::DetectionLimitSimple( MaterialDB *materialDB,
   m_fwhm( nullptr ),
   m_fwhmSuggestTxt( nullptr ),
   m_addFwhmBtn( nullptr ),
+  m_selectDetectorBtn( nullptr ),
   m_continuumPriorLabel( nullptr ),
   m_continuumPrior( nullptr ),
   m_continuumTypeLabel( nullptr ),
@@ -450,10 +451,18 @@ void DetectionLimitSimple::init()
   
   m_fwhmSuggestTxt = new WText( generalInput );
   m_fwhmSuggestTxt->addStyleClass( "FwhmSuggest GridThirdCol GridSixthRow GridVertCenter GridSpanTwoCol" );
+  
   m_addFwhmBtn = new WPushButton( WString::tr("dls-fit-fwhm-btn"), generalInput );
   m_addFwhmBtn->clicked().connect( this, &DetectionLimitSimple::handleFitFwhmRequested );
   m_addFwhmBtn->addStyleClass( "MdaFitFwhm LightButton GridFifthCol GridSixthRow" );
   
+  m_selectDetectorBtn = new WPushButton( WString::tr("dls-select-drf-btn"), generalInput );
+  m_selectDetectorBtn->clicked().connect( this, &DetectionLimitSimple::handleSelectDetectorRequested );
+  m_selectDetectorBtn->addStyleClass( "MdaFitFwhm LightButton GridFifthCol GridSixthRow" );
+  
+  const shared_ptr<const DetectorPeakResponse> drf = m_detectorDisplay->detector();
+  m_addFwhmBtn->setHidden( !drf || !drf->isValid() || drf->hasResolutionInfo() );
+  m_selectDetectorBtn->setHidden( drf && drf->isValid() );
   
   m_continuumPriorLabel = new WLabel( WString::tr("dls-deon-cont-norm-label"), generalInput );
   m_continuumPriorLabel->addStyleClass( "GridFirstCol GridSeventhRow GridVertCenter" );
@@ -631,13 +640,15 @@ void DetectionLimitSimple::setFwhmFromEstimate()
   
   float fwhm = 0.1f;
   const shared_ptr<const DetectorPeakResponse> drf = m_detectorDisplay->detector();
+  
+  m_addFwhmBtn->setHidden( !drf || !drf->isValid() || drf->hasResolutionInfo() );
+  m_selectDetectorBtn->setHidden( drf && drf->isValid() );
+  
   if( drf && drf->hasResolutionInfo() )
   {
-    m_addFwhmBtn->hide();
     fwhm = drf->peakResolutionFWHM( energy );
   }else
   {
-    m_addFwhmBtn->show();
     fwhm = std::max( 0.1f, PeakSearchGuiUtils::estimate_FWHM_of_foreground(energy) );
   }
   
@@ -665,11 +676,11 @@ void DetectionLimitSimple::handleUserChangedFwhm()
     m_fwhm->setValue( fwhm );
   }//if( invalid FWHM )
   
+  m_addFwhmBtn->setHidden( !drf || !drf->isValid() || drf->hasResolutionInfo() );
+  m_selectDetectorBtn->setHidden( drf && drf->isValid() );
   
   if( drf && drf->hasResolutionInfo() )
   {
-    m_addFwhmBtn->hide();
-    
     const double drf_fwhm = drf->peakResolutionFWHM( energy );
     if( fabs(fwhm - drf_fwhm) > 0.1 )
     {
@@ -683,7 +694,6 @@ void DetectionLimitSimple::handleUserChangedFwhm()
     }
   }else
   {
-    m_addFwhmBtn->show();
     const float est_fwhm = std::max( 0.1f, PeakSearchGuiUtils::estimate_FWHM_of_foreground(energy) );
     
     char text[32] = { '\0' };
@@ -1084,6 +1094,9 @@ void DetectionLimitSimple::handleDetectorChanged( std::shared_ptr<DetectorPeakRe
   //  to date.
   m_detectorDisplay->setDetector( new_drf );
   
+  m_addFwhmBtn->setHidden( !new_drf || !new_drf->isValid() || new_drf->hasResolutionInfo() );
+  m_selectDetectorBtn->setHidden( new_drf && new_drf->isValid() );
+  
   handleUserChangedFwhm();
   
   m_renderFlags |= DetectionLimitSimple::RenderActions::UpdateLimit;
@@ -1102,6 +1115,12 @@ void DetectionLimitSimple::handleFitFwhmRequested()
 }//void handleFitFwhmRequested()
 
 
+void DetectionLimitSimple::handleSelectDetectorRequested()
+{
+  m_detectorDisplay->editDetector();
+}//void handleSelectDetectorRequested()
+
+
 void DetectionLimitSimple::handleSpectrumChanged()
 {
   m_renderFlags |= DetectionLimitSimple::RenderActions::UpdateLimit;
@@ -1578,13 +1597,10 @@ SimpleDialog *DetectionLimitSimple::createDeconvolutionLimitMoreInfo()
   WTable *table = new WTable( contents );
   table->addStyleClass( "DeconvoMoreInfoTable" );
   
-  
-  
-  
   const auto print_result = [table, use_curie, measurement, roi_start, roi_end]( 
                                         const DetectionLimitCalc::DeconComputeResults &result,
                                         const bool is_best, const WString typestr ){
-    WString label = WString("{1} {2}").arg(typestr).arg( WString::tr("dls-Limit") );
+    WString label = WString("{1} {2}").arg(typestr).arg( WString::tr( (is_best ? "Activity" : "dls-Limit") ) );
     WString value = PhysicalUnits::printToBestActivityUnits( result.input.activity, 3, use_curie );
     
     WTableCell *cell = table->elementAt( table->rowCount(), 0 );
@@ -1593,7 +1609,7 @@ SimpleDialog *DetectionLimitSimple::createDeconvolutionLimitMoreInfo()
     new WText( value, cell );
     
     
-    label = WString("{1} {2}").arg(typestr).arg( WString::tr("dls-Limit") );
+    label = WString("{1} {2}").arg(typestr).arg( WString::tr( (is_best ? "Counts" : "dls-Limit") ) );
     double counts = 0.0, uncert = 0.0;
     for( const auto peak : result.fit_peaks )
     {
@@ -1762,6 +1778,8 @@ SimpleDialog *DetectionLimitSimple::createDeconvolutionLimitMoreInfo()
     //                " source before any shielding, but accounting for nuclide age,"
     //                " per decay of the parent nuclide." );
   }//if( branch_ratio > 0.0 )
+  
+  return dialog;
 }//void createDeconvolutionLimitMoreInfo()
 
 
diff --git a/src/DetectionLimitTool.cpp b/src/DetectionLimitTool.cpp
index 42b33590..c0a5b75d 100644
--- a/src/DetectionLimitTool.cpp
+++ b/src/DetectionLimitTool.cpp
@@ -2045,6 +2045,51 @@ SimpleDialog *DetectionLimitTool::createCurrieRoiMoreInfoWindow( const SandiaDec
                     " expected to lead to detection." );
     
     
+    switch( limitType )
+    {
+      case DetectionLimitTool::LimitType::Activity:
+      {
+        if( result.source_counts <= result.decision_threshold )
+        {
+          // There is NOT enough excess counts that we would reliably detect this activity, so we
+          //  didnt give nominal activity above, so we'll do that here
+          WString obs_label;
+          string lowerstr, upperstr, nomstr;
+          if( drf && (distance >= 0.0) && (gammas_per_bq > 0.0) )
+          {
+            obs_label = "Activity";
+            const float nominal_act = result.source_counts / gammas_per_bq;
+            
+            nomstr = PhysicalUnits::printToBestActivityUnits( nominal_act, 2, useCuries )
+                      + DetectorPeakResponse::det_eff_geom_type_postfix( det_geom );
+            if( nominal_act < 0 )
+              nomstr = "< " + PhysicalUnits::printToBestActivityUnits( 0.0, 2, useCuries )
+                        + DetectorPeakResponse::det_eff_geom_type_postfix( det_geom );
+          }else
+          {
+            obs_label = "Observed counts";
+            nomstr = SpecUtils::printCompact(result.source_counts, 4);
+            
+            if( result.source_counts < 0 )
+              nomstr = "&lt; 0 counts";
+          }//if( drf ) / else
+          
+          nomstr += " <span style=\"font-size: smaller;\">(below L<sub>c</sub>)</span>";
+          
+          cell = table->elementAt( table->rowCount(), 0 );
+          new WText( obs_label, cell );
+          cell = table->elementAt( table->rowCount() - 1, 1 );
+          new WText( nomstr, cell );
+          addTooltipToRow( "The observed signal counts is less than the &quot;critical level&quot;, L<sub>c</sub>,"
+                          " so a detection can not be declared, but this is the excess over expected counts/activity." );
+        }//if( result.source_counts <= result.decision_threshold )
+      }//case DetectionLimitTool::LimitType::Activity:
+        
+      case DetectionLimitTool::LimitType::Distance:
+        break;
+    }//switch( limitType )
+    
+    
     // Add a blank row
     cell = table->elementAt( table->rowCount(), 0 );
     txt = new WText( "&nbsp;", TextFormat::XHTMLText, cell );
diff --git a/src/PeakSearchGuiUtils.cpp b/src/PeakSearchGuiUtils.cpp
index cd3b0010..933e63e1 100644
--- a/src/PeakSearchGuiUtils.cpp
+++ b/src/PeakSearchGuiUtils.cpp
@@ -3131,7 +3131,7 @@ std::pair<std::unique_ptr<ReferenceLineInfo>,int> reference_line_near_peak( Inte
       const double dist = fabs( l.m_energy - mean );
       const double w = l.m_normalized_intensity / (0.25*sigma + dist);
       
-      if( (w > largest_w) && (l.m_energy < ux) && (l.m_energy > lx) && (dist < 4*sigma) )
+      if( (w > largest_w) && (l.m_energy < ux) && (l.m_energy > lx) && (dist < 5*sigma) )
       {
         largest_w = w;
         best_energy = l.m_energy;
@@ -3183,8 +3183,30 @@ float reference_line_energy_near_peak( InterSpec * const interspec, const PeakDe
 tuple<const SandiaDecay::Nuclide *, double, float>
     nuclide_reference_line_near( InterSpec *viewer, const float energy )
 {
-  const double sigma = estimate_FWHM_of_foreground( energy );
-  
+  double sigma = estimate_FWHM_of_foreground( energy );
+  
+  // For HPGe zoomed out, its really hard to be within the 5-peak-sigmas of the reference
+  //  line that `reference_line_near_peak(...)` requires, so we'll also take into account
+  //  the number of pixels a peak would show up as.
+  //  Note: `SpectrumChartD3.prototype.updateMouseCoordText(...)` basically requires within 10px
+  const shared_ptr<const SpecUtils::Measurement> hist
+                = viewer->displayedHistogram(SpecUtils::SpectrumType::Foreground);
+  if( PeakFitUtils::is_high_res(hist) )
+  {
+    double xmin, xmax, ymin, ymax;
+    viewer->displayedSpectrumRange( xmin, xmax, ymin, ymax );
+    
+    const int ww = viewer->renderedWidth();
+    
+    if( (xmin < xmax) && ((xmax - xmin) > 50.0) && (ww > 200) )
+    {
+      // Will assume chart plot-area is 100px narrower than total window (unchecked).
+      const double keV_per_pixel = (xmax - xmin) / (ww - 100);
+      // set peak-sigma to be 2 pixels, giving us to require 10 pixels of accuracy from the user
+      sigma = std::max( sigma, 2.0*keV_per_pixel );
+    }//if( x-range and render size seem reasonable )
+  }//if( PeakFitUtils::is_high_res(hist) )
+      
   PeakDef tmppeak( energy, std::max(sigma,0.1), 100.0 );
   
   const pair<unique_ptr<ReferenceLineInfo>,int> refline