It would seem for simplicity's sake a powder that does not require fillers of any kind would be preferable to one that does, unless as I have experienced and Daryl notes, the wad is used for some other purpose; elimination of leading, for example.

I'd encourage anyone who has a need for a large-case Black Powder-velocity load to look closely at Accurate 5744. That stuff has served me well in .45-70 and I've read of very good results in other larger cases, too.

Only caveat is that I can't say whether or not safe working pressures would exist with certain bullet weight/velocity duplication charges, meaning, simply, use all normal care and safe loading practises in working up loads.

A load I've used in my Marlin with excellent results uses 5744 plus a 420 grain Lyman flat point bullet for 1600 fps. This is the beginning threshold for stiff recoil in the Marlin, but such a load is a very deep penetrator and seems ballistically quite similar to some of the NFB performance loads discussed here from time to time. Of course, many modern .45-70 loads duplicate the performance of much bigger British BP cases.