Hes 15 =]
He's looking brill, for the first time since owning him, when I was riding my other horse as per usual I had him free grazing (its a massive flat paddock, and he normally just grazes, instead he had a MASSIVE blat around the paddock, jumped some x-c jumps, leaped, bucked, farted, spun and just galloped up and down nd up and down =D
Yes, he was definitely a little on the thin side & you've done well beefing him up. Also obvious you've been working on getting him fit & better muscled. I agree that muscles could be better, especially on his butt - hill work is great for that - but I don't agree he needs more weight generally.