If your going to use T-7 as the main charge, you will have to duplex the load. Dump 10-20 grains of black powder down first. Also remember to clean that touch hole real well. You might still encounter some ignition problems in damp wet weather. Personally I would use 2f black powder as the main charge and 4f as the pan primer.

I also agree that 4f as the main charge depending on the amount he is using might be a little much. Also the concern of it coming out the touch hole if the rifle is tipped. Instead I would use 2f. But hey, if it works for him, who am I to say.

When I shoot my Lyman, Thompson Centers, or Tradition flintlocks, I use 2f in all but the Traditions. That likes 3f as the main charge and its always black powder. 3f will also work in the pan in you have no 4f.