I love the .54 also. So I'll tell ya my story(short) about them ball.
I shoot Dutch. Cut at the muzzle dry-lube patch. The system works great! Anyway's, I had found a combo of lube and a .021/.011 crushed denim with a .535. ball that gave me 1" bench groups at 50( talk about confidence), trouble is I only had 2 yrds of that cloth!
Well, I had "too soon" found myself running out of patch material. I looked in every fabric shop in a 60 mile radius trying to find the same and finally found something close. The "close" fabric didn't work well at all!(crushed thicker .0115) I had to change to a .530 ball and increase the lube to find the same happy 1" group I know and trust.
Moral of the story, and lesson learned is; it don't matter which variable you change,.530 or .535 ball size still has to be wraped with a patch that has a lubrication. Personal experience lends a snug fitting patch with a dryish lube is most accurate.
Which mold? I guess 530 is most common,,easiest to practice with while learning consistant cast and still maintain re-sale value.
luck to ya,
ps. i got a few horns here and onna them "priming" valve thingy's i'll send ya fer (easy enough ta do your self)..PM we'll swap e-addy's