I know this is 2 months later, but as far as I know, str, sta and size factor into hp. Other then race.
I think i saw somewhere about how much exactly is one str-hp(sa &size), try looking around here sonewhere.
Something like 3 or 4 hp per str, 7-8 per sta and 10 per size.
But i am just talking out of my ass now, sooooo better check. xD