Dang SH that is a adventurous endeavor you're going after. Seems to me to be just too much trouble for a front stuffer and then use smokeless powder. IMO it's not much different that a single shot CF. I'm thinking myself of getting one of the single shot Henrys coming out in May in .45-70 and using BP in it. That should be an easy one to clean up after a day of shooting BP.
But to each their own and if you go through with it I wish you the best.