I like his rear end. Can't tell "Cat Ballou" (love that film!!), if he's downhill?
IMO, I hate the "new" rear end that is being bred on halter QH's. Looking overly muscled is NOT the same as having a muscled up rear end. They started this crap about 30 years ago, breeding a tiny foot on a bulldog type, and pretending that it could support all that extra weight. ALL about looks, just like dog breeds, and nothing really different about performance.
Sorry for the rant but these horses have to LIVE with these genetics, and I think they are a step backwards.
You horse looks functional, and I like that.