I started at 80gr ffg with a .530" PRB in .015" pillow ticking. My current "hunting load" is 90gr fffg Goex under the same ball/patch combo and shoots as well as I can hold the rifle.
Yo Boker.
The .54 New Englander is about the same as the TC Renegade with regards to the inside of the barrel.
Some people find that .54 TC's work best with a 120 grains of FFg and patched round ball. That was my brothers experience... actually he fiddled with it until he got max loads to give tack driver accuracy because those were the parameters he wanted. My TC .54 made me crazy because the QLA cut the patches and I ended up having it sleeved to .458 bore with a 24" twist and put a TC New Englander peep sight on it. Yes, it's nice, though slimming down the stock is on the rework list.
I'll have to work with the .50 a bit. I've tired .490s with patches from .015" -.025", ffg, fffg, and different lubes. .495s will be next. OTOH, the .54 shot PRBs great from the start, ffg or fffg, and doesn't seem the least bit finnicky.