My friends horse could jump 3'6 at home, but I would suggest to try out smaller at about 2ft3 classes. My friends pony is the same size as yours, and was a great jumper, but when he got to the competition it blew his mind, to atmosphere made him not concentrate at all. But after a few shows he gained confidence and got used to it all and would jump 3ft classes and 3'6 classes.Start out small and get bigger, and you will soon find out his limit. Just practice and practise! he looks like a brilliant jumper! and his legs look great!