You can't really judge comfo when the horse is in motion & side shots are good.
However, just going by what you've got, his front feet are quite close together & his backs wide apart.
His back is a little long & looks like he may be wither high, but i've found that to be quite common in OTTB's, especially the tall ones.
His neck looks a bit long due to a lack of muscling but I like his shoulder & butt from these pics.
Do they even make a Mr Prospector kid without a one white sock leg? It's so cute. I don't know about the other horses in his line as far as temperment, but the Mr. Prospector horses are the best in terms of work ethic and personality.