The one hanging on the wall in the living room has a paw about 4" and was right around 200# the two I field dressed for friends last year were each over 300# one field dressed right at 300 and the other was bigger but was never weighed on an official scale, I' d say he dressed at about 350. We never did measure the paws but the larger one green scored a 19" skull.
Plainsmans formula seems reasonable but I have never heard of it before, but that doesn' t mean anything. There are a lot of things I have never heard of before.
Black Bears range in color from jet black to pure white with just about every shade of black and brown in between. The wife of a friend killed one in CO years back that was a beautiful cinnamon shade.
There is one in the area that guys swear has a 9" track which would put him in the 450# range which is not extraordinary for this area. Some lady killed one on the road with her Toyota a few years back that went right around 560 which was the largest killed in the state.