Some good bell boots will do the trick if he doesn't stop doing it after the adjustment. The bell boots shouldn't cause any problems either so long as they fit well.
I ride my boy in Horze no turn over-reach boots, neoprene ones and no more scarred up heels, and he moves better with the slight weight of them on, and he also feels more confident when he knows he has them on.
That can be a problem if you want to put shoes on though, one of my friends horses does that and was constantly pulling his shoes off with the other hoof, granted the farrier wasn't one I would have chosen, but he was still ripping them off no problem. The farrier ended up shoeing him for free because they couldn't figure out what was happening to all these shoes.