From @tlatham: The other thing that I notice, which perhaps we should deal with when we also start to include other existing models into this new mini-framework for semi-leptonic models (to remove existing code duplication), is that the responsibility for checking the number of arguments, etc. is different for the BGL and BCL cases. The BGL has constructors that accept a specific number of arguments and the check is made by the EvtBToXElNu::init function, while the BCL constructor receives an array and the number of elements and makes the checks itself. I think the latter option is preferable (although perhaps ideally using a vector instead of the array) because the EvtBToXElNu class shouldn't need to know the details of how each FF works, that should be up to the FF class itself. Either way, we should pick a single approach and stick to it for all cases.