Blackbearhunter,
I grabbed my old manual that came with my .54 cal New Englander---has all the loading info from TC in it.
For the .50 cal maxi ball (370 gr) or maxi hunter (355 gr) the manual lists 80 grains as start 1271fps
90 grains 1344fps
100 grains max 1418fps
Hope this info helps!