diff --git a/analyses/pluginMC/MC_WEIGHTS.cc.hmmmmmm_interesting b/analyses/pluginMC/MC_WEIGHTS.cc.hmmmmmm_interesting
--- a/analyses/pluginMC/MC_WEIGHTS.cc.hmmmmmm_interesting
+++ b/analyses/pluginMC/MC_WEIGHTS.cc.hmmmmmm_interesting
@@ -1,86 +1,73 @@
 // -*- C++ -*-
 #include "Rivet/Analysis.hh"
 
 namespace Rivet {
 
   /// @brief Analysis for the generated cross section
   class MC_WEIGHTS : public Analysis {
   public:
 
     /// @name Constructors etc.
     //@{
 
     /// Constructor
-    MC_WEIGHTS()
-      : Analysis("MC_WEIGHTS")
-    {    }
+    DEFAULT_RIVET_ANALYSIS_CTOR(MC_WEIGHTS);
 
     //@}
 
 
   public:
 
     /// @name Analysis methods
     //@{
 
     /// Book histograms and initialise projections before the run
     void init() {
       /// @todo Convert to Scatter1D or Counter
-      _h_weight_100 = bookHisto1D("weight_100", 200, -100.0, 100.0);
-      _h_weight_10  = bookHisto1D("weight_10", 200, -10.0, 10.0);
-      _h_logweight_pos  = bookHisto1D("logweight_pos", logspace(100, 0.1, 10000.0));
-      _h_logweight_neg  = bookHisto1D("logweight_neg", logspace(100, 0.1, 10000.0));
+      book(_h_weight_100, "weight_100", 200, -100.0, 100.0);
+      book(_h_weight_10,  "weight_10",  200,  -10.0,  10.0);
+      book(_h_logweight_pos, "logweight_pos", logspace(100, 0.1, 10000.0));
+      book(_h_logweight_neg, "logweight_neg", logspace(100, 0.1, 10000.0));
 
-      _h_xsfraction_neg   = bookScatter2D("xsfraction_neg");
+      book(_h_xsfraction_neg, "xsfraction_neg");
 
-      _sow_pos = _sow_neg = _nevts = 0.;
+      // Maybe something like this could work?
+      _h_weight_100->fill_all_weights();
+      _h_weight_10->fill_all_weights();
+      _h_logweight_neg->fill_neg_weights();
+      _h_logweight_pos->fill_pos_weights();
     }
 
 
     /// Perform the per-event analysis
-    void analyze(const Event& event) {
-      double w = event.weight();
-
-      _nevts += 1.0;
-      _h_weight_100->fill(w, 1.0);
-      _h_weight_10->fill(w, 1.0);
-      if (w<0.0) {
-        _h_logweight_neg->fill(fabs(w), 1.0);
-        _sow_neg += fabs(w);
-      }
-      else {
-        _h_logweight_pos->fill(w, 1.0);
-        _sow_pos += w;
-      }
-    }
+    void analyze(const Event& event) {  }
 
 
     /// Normalise histograms etc., after the run
     void finalize() {
-      scale(_h_weight_100, 1.0/_nevts);
-      scale(_h_weight_10, 1.0/_nevts);
-      scale(_h_logweight_pos, 1.0/_nevts);
-      scale(_h_logweight_neg, 1.0/_nevts);
+      const double sf = 1.0 / numEvents();
+      scale(_h_weight_100, sf);
+      scale(_h_weight_10, sf);
+      scale(_h_logweight_pos, sf);
+      scale(_h_logweight_neg, sf);
       /// @todo correct unc estimate:
-      _h_xsfraction_neg->addPoint(0, _sow_neg/(_sow_neg+_sow_pos), 0.5, 0.0);
+      const double negFrac = _h_logweight_neg->sumW() / (_h_logweight_neg->sumW() + _h_logweight_pos->sumW());
+      _h_xsfraction_neg->addPoint(0, negFrac, 0.5, 0.0);
     }
 
     //@}
 
 
   private:
 
     /// @name Histograms
     //@{
     Scatter2DPtr _h_xsfraction_neg;
     Histo1DPtr _h_weight_100, _h_weight_10, _h_logweight_pos, _h_logweight_neg;
-    double _sow_pos, _sow_neg, _nevts;
     //@}
 
   };
 
-
   // The hook for the plugin system
   DECLARE_RIVET_PLUGIN(MC_WEIGHTS);
-
 }