I have a gelding appaloosa. I love him to death but he seems to be just a little 'narrower' than most horses. I'm not sure how to explain it, but he is very tall and not very wide if that makes sense. He also doesn't seem to have as much of a sway in his back like most horses do. Anyways, When I get him up to a lope, the only way I can stay on is to hang onto the horn. I feel like I'm going to just go off the side at any second unless I am holding on for dear life! Is this because he is not very wide and doesn't have much of a dip in his back or am I doing something wrong? Is it the saddle? I am a fairly new rider but I can lope with my friends horse fairly easily with both hands on the reins. Any suggestions?