This is right from the web site for using Triple Seven in a flintlock:

Flintlock: To insure proper ignition in flintlock systems, 5 grains of FFFFG priming powder should be placed into the bore prior to loading the main charge of Triple Seven, Consult the loading data in this brochure to determine the proper charge for the caliber firearm used and the chosen projectile. The main powder charge should be reduced by 5 grains to compensate for the addition of the priming powder. While holding the firearm vertically, slowly pour the measured charge of Triple Seven into the barrel. Seat the projectile firmly against the powder. Make certain that there is no airspace between the powder and the projectile.

They don't make 4f Triple Seven so they must mean 4f black powder.
The Pa Pellet has a removable breech plug and 5 grains of 4f does not fill the plug up to the touch hole. That's why I use 10 grains and cut the main charge from 90 grains to 80 grains.