Awesome!! How many hands high is he???
And if you're easy to buck off, shorten your stirrups one or two notches, and when you're sitting in the saddle, sit up straight & push your heels down. If your heels are down & toes are up, it's a LOT harder for your ass to budge anywhere.
The difficult part is keeping heels down without your toes sticking out to either side & up.
Give it a try, you'll see.
Is he just green broke?