I don't know whether it's lordosis or just a really funky "bubble butt" that I'm seeing. It's like the point of his croup is really bulgy.
His front legs are good and clean with pasterns that are a nice length and angle. He's a bit long through the gaskin, which leaves him a little camped out. His shoulder is a little upright and his croup is a little steep. He looks like he might have a bit of a ewe neck when he looses the studdy crest.
I think he'll make a very nice gelding...and I am so glad you're making the decision to have that done.
He doesn't look all that thin to me. It wouldn't hurt to see a little more weight on him, but I wouldn't call him skinny.
I'm definitely seeing some sway back though, likely genetic since he's so young- so its good that you will be gelding him soon. Shame that he wasn't gelded earlier, so that the big bulky neck could have been avoided...I think it would have helped his over all presentation. Dispite the sway though, I do think he has a nice big hip, and straight (though light) legs until you get to his pasterns. The pasterns are too long IMO and his front feet look overgrown. Hard to see his shoulder, but it looks on the straight side to me.
Over all, not an aweful horse provided that his sway doesn't become sway (make sure you condition him right and fit his saddle well to prevent soreness) but he definitely needs to be gelded; the sooner the better.
I do really like his face. He looks sweet and the facial markings and color really remind me of our big foundation bred QH mare. She's much stouter than your guy though, and almost has too short of a back xD
I'd like to see him on level ground. But from this pic, he doesn't show a ton of balance. While I like his pasterns..the length and angle on all four, he lacks depth in bone in all 4 cannons. Short neck that doesn't match the rest of his body, steep but very short croup as evidenced by his tailset, weak across the topline. I would like to see a better pic. Have someone set him up on level ground and hold him for you, his head straight, feet squared...and the photo taken with you standing dead center of his barrel.