I shoot a .54 CVA Hawkens, and boy, is it a joy to work with. Mine's not very picky at all. 'Seems to group just about any configuration of load to about 2" at 100 yards. I'm running 110 grains of FF under a patched .530 roundball. Brand of lubricant seems to make no difference, and I think if I remember correctly I'm shooting 0.15 thickness patches. I tried cotton t-shirt material but felt like it was a little too loose, and the patches would burn out too much. I've hunted with this gun for over 20 years. I had the trigger group gone over one time, and I shoot a Hot Shot nipple. Other than carrying a heavier ramrod with me, the gun's just as it came off the line. Fun to hunt with and a joy to shoot.
Try some FFF though yours just for giggles. I found that it grouped very tight at 50 yards with the FFF, but dropped more than I was satisfied with at 100. Good luck and let us know how it shoots.