He does have a long back and body as you noted.
From a juming viewpoint he does possess some positives. Namely the longer limbs and higher placed knee which encourages an easier and higher limb lift. The shallower girth which keeps the upper body lighter and therefore easier to lift. This also allows freedom for the limbs below encouraging stride extension. He also has what appears to be a slightly upright blade, which may alllow for further blade slope backwards when jumping and perhaps landing. Nice moderate/long pasterns add jumping spring and suspension. Lovely head and shading. Nice strong Thoroughbred muscle shape. On the flat I also see some potential for the desired expressive movement. Good luck