The only thing I don't really like about her build is her neck, it needs muscle.
Possibly a little bum high
And she's a tad posty in the back legs and her hocks are low, but other than that she is built fairly decently.
Nice shoulder angle and good depth through the chest
Front legs look ok
Back, I think, I borderline long but not bad
Small hindquarters but not badly shaped
I like all of her except her legs... I don't know why, but they look a bit... flimsy to me. I feel like they're a little too light. They have nice canon bone/ pastern length, the fronts seem pretty straight although so do the backs, but they just don't seem to have enough substance....
Otherwise, she has a nice shoulder with a pretty nicely tied in neck (correct me if I'm wrong, I'm no expert), with a wither that looks well laid back, a decent length of back, an okay hip (it could be a little bigger, but I think it fits her well as is) with a decently sloped croup and a deep girth. Her body looks well-balanced overall. Other than her legs, I do think she's a good looking horse, although I can't say whether she'll be any good for HUS.
I feel like it's probably because her fetlocks seem pretty low, plus her straight hind legs. I don't know, it may just be me that thinks her fetlocks are too low anyway, haha.
The more I look at her legs, the more I don't like them. Her fronts look like they bend inwards, although it might just be the camera angle... I'm starting to wonder if her pasterns are a smidge too long/ or too angled, also, for some reason what I can see of them looks weak to me.
I picked D before I read your last sentence! Ok... I think I see that too. So with a post legged horse would that be more suited for a shortened stride like a western pleasure style or would it not really effect movement?