Yes, those are actually much better photos, thanks!
The one thing that would seriously concern me about putting this horse in a high-impact sport like barrels is that he is very over at the knee...in photo #2, compare his front legs to the bay he is standing next to and it is very obvious. This is going to but a lot of stress on his tendons with fast, hard impacts and could lead to bowing and other tendon injuries. His shoulder is not as steep as it looked in the other photos...could be better, seen worse. I would still say his back is long. Exercise will improve how he carries himself (and you) but I don't know how that will affect him making tight turns on a barrel, maybe some of the barrel racers in the crowd can comment on that?