Shotput,wool wads work well put right on the powder. Saturate them with a lube/wax combo that's not runny and won't squish into the powder when seating the ball.
A good way to avoid any consternation about how deep a ball is seated in the chamber with target loads(the most accurate isn't always the most powerful.....I know you know that) is to have a machinist/gunsmith ream yer chambers to be the diameter of the grooves in the barrel while also ridding the chambers of irregularities and taper.
You'll get better accuracy that way and be able to use any acceptable powder load without concern.
I have a milling machine and chucking reamers(four flute/straight flute) and a centering tool I had Starret makes for me. Works well enough. Straightens the taper that can be in the chambers and the irregularities.
Irregularities like you wouldn't imagine in those chambers of the Italian guns. It shows at times when a good chucking reamer is run into a chamber at a certain minimum diameter as ......a shiny chamber with black(the bluing) still showing in places on the side walls of the chamber. The black left is where the chamber walls were irregular and had wide spots like the chamber wasn't round to begin with.
Accompaning a chamber sizing/reaming is a fresh up of the forcing cone of the breech end of the barrel. A forcing cone of 11 degrees works well to fresh it up and makes it concentric with the bore for better accuracy(when using a piloted reamer that has a pilot that actually fits snug in the bore).
Accompaning that would be a check/repair(if needed) of the alignment of the chambers to the bore for better accuracy.
Do those things and worry over the seating depth of the ball with certain powder charges/fillers ect.ect. are over.
I target shoot cap&ballers too. I get good accuracy. I don't do minute of angle or the like. I do minute of rock,stump,ground hog,fence post ect.ect.ect.