i think it looks fine if it were any closer it would be on the horses shoulder and limiting his movement
but it can be hard to tell when theres not much of a wither
my friends pony is round like that and i'm pretty sure that is about where she has her saddle
but i may be wrong so anyone correct me if i am
It looks a tad too far back, but only by about an inch. The point of three (you can see it in a little square "pocket" under the flap, above the knee roll) should be 2-3" behind the back edge of the shoulder blade.
If the horse likes it there and you feel comfortable riding, then leave it! ;-)