Jerry and I can do jumps up to 2 feet fairly decently. We have those random refusals every now and again, and my position is near perfect. But when we raise it to 2'3, I brace with me heels. I kind of stand up in the stirrups, and my heels come up. I don't know why I do it, (my stirrups are short enough), but I would like to know how I can fix it.