As I've been working with both squirrels (B and S) I found I needed define them more in terms of their traits so their designs could be less broad and more character specific, so here's a little about both characters.
S is a leader, he isn't strong but he's smart he uses his wit to get him out of most situation, he fast on his feet, and he has a bit of an anger issue, he looses his temper very quickly and is very selfish, if he had to choose between one acorn or two, he'll pick two and slap you for asking a dumb question
B is a follower, he is very strong but simple minded he observers things as though they were new to him and he's slow but he more than makes up for it with his strength, B is kind but when he wants something he'll do anything to get, normally he wouldn't hurt a fly but he'll trample on a family of flies to get hold of a shiny balloon he likes, if he had to choose between one acorn and two acorns, he'll pick two because he wouldn't want the other acorn to be lonely.
A few character traits that affect their design
He's got a part of his left ear bitten off (lost it in a fight?), and is tails more jagged it reacts depending on how angry he is
He's a lot more rounder and his lack of experience causes him to do things in very differnt way, so doesn't use his hand very often so his tail curls up like a fist for grabbing things, and his hands and significantly smaller than S's
These are my current two Influence Maps for both characters.