Simultaneous RooDataHist

Dear RooFit experts.

I am trying to fit a RooSimultaneous, build up of four categories, and
will need to create a RooDataHist from some TH1 histograms.

The problem arises (at least partially) because the observables in the different channels
of the pdf does not have the same name, as is the case for all the examples I have managed to find.

I have attached a very small piece of example code that illustrates how I’m building my RooDataHist.
The code technically works but the thing I don’t understand is why the resulting RooDataHist (combData) ends up having 3000000 bins (seems that the number of bins goes as n_Channel * (10*N_TH1_bins) ^ nChannel).
The actual analysis has 400 bins in each histogram and four channels so this is of course not possible to use.

I think I’m doing something wrong here, as I would have thought that the number of bins
should just be n_Channel * n_TH1_bins.

Thanks in advance.

Best regards,

(If there are smart ways to create Asimov data from a Simultaneous pdf,
that could also be a solution)
rooHistPdfTest.C (1.41 KB)