My Deerstaker is a .54 percussion. It is very accurate with 90 grains FFG Goex, .530" Hornady roundball, with .018" pillow ticking patch, lubed with Hoppes #9 Plus Black Powder Solvent And Patch Lube. Great gun, one of my most accurate MZ's.
I like the Maxi Hunters because they load so easy-----I short start them with my thumb and then they seat easily with the ramrod.
The Maxi hunters have been discontinued by T/C BUT you can find them if you look around. I have bought 10 boxes from all over!!!
My best groups are with the patched round ball in my .54 Deerstalker. I am currently using 85 grains of 2f Goex, Crisco for lube, .015 patch and 530 ball with 4f for the pan. I use Hoppes plus for patch lube at the range.
If you are cutting patchs and suspect sharp rifling use a 30 cal bore brush and cut a patch out of a Scotch Brite pad to fit around the brush and run it up and down the bore about 25 times.
I've had great accuracy and performance from the 348gr and 400gr powerbelts and about 90gr of 2F (any more than that and accuracy went out the window). Picked up some hornady GP's but haven't tried them yet.