Kate
DH & I looked at your picture. She is not standing square, so it is a little deceiving. Her hind legs are under her pretty far in the picture, so it looks like her gaskin muscle isn't very long, it may just be the picture, or it could be from lack of exercise. If her personality matches her looks, she will be great.
I don't worry about a pot belly, that will go away when she goes to work.
DH said that is a pretty darn good mare. He doesn't say that very often, either. We don't ride English, so when I told him what you were planning on doing with her, he said "you don't put an English saddle on a horse like that" He also said if you knocked her head open, cows should fall out!! She has very good bloodlines. She is bred to work cattle.
I read the other comments to him & he said he sure would breed her if he had her.
She is a bulldog built mare, just our type. I hope she meets with what you are looking for. Let us know how it goes.
Jean