well as i recall, weight penalty to profiency is:
body armor: 1 weight point = 1 WPF
legs armor: 1 weight point = 1 WPF
hands armor: 1 weight point = 2 WPF
head armor: 1 weight point = 3 WPF
if total armor weight is under 6 points, no penalty at all (example using only a studded leather 5 weight armor will not give you any penalty to wpf. but adding 2 weight points will reduce your wpf by 7 as you have 7 weight points on you.)
anyway the cRPG builder program had a wpf penalty calc inside... but was a program made by poul several months (and patches) ago.