[Rivet] Shape comparisons

[James Henderson]

Dear Rivet Experts,

I have recently updated my Rivet version to 1.8.0 and it seems that now 
Rivet is able to automatically read in the cross-section of a sample 
straight from the HepMC file. I was trying to normalise two sample with 
different actual cross-sections to 1pb in order to do a shape comparison 
but I can't seem to overwrite the automatic cross-section finder.

Is there a way to do such a shape comparison without explicitly altering 
the .cc file in order to not normalise to the cross-section?

Thanks,
Jim