This might not be something you want to try, but we went with kicking chains on a couple horses who were “light in the rear” when they were a. Impatient b. Ticked off c. Touched unexpectedly d. Felt threatened from behind. Totally unacceptable here!
We have a center aisle barn, tie stalls on one side, so 4 rumps aimed at the aisle where we harness and hitch everyone. Lots of activity going on behind them. Plus the tie stalls have folks walking in and out on both sides of the horse to feed and water, getting horse out or putting horse in, then leaving. Can NOT have a kicker or horse who kicks when surprised, people get hurt that way!
I have found the kicking chains to be an excellent training tool to fix the stalled horse problems and so far, much of it transfers to their being driven too. Any punishment is self-inflicted, stops when horse quits kicking. No damage to legs on my horses. Chains are hung from straps above the hocks, not touching the ground to get stepped on.
I do not like the bent horse shoes around the pasterns for stopping kicking. All the ones I saw left the ankles rubbed sore. 3 of 4 horses here wore the chains “awhile” and did not kick again when we quit using them a couple months later. The 4th horse would kick her stall wall if the chain was off, so she wore them until she got sold a year or 2 later. We did not do things to suit her! Ha ha
I would totally second and third using a kicking strap when your pony starts getting hitched and for a long time after! He may need the strap forever in his driving career. Some do if a kick is their “go to” method of expressing displeasure over something. Probably not going to change a habit on an older animal. But having the kicking strap on is not a disgrace! You may get asked about it, people always wonder when they see something done differently. Say he is just green. Better safe than sorry! I have seen kicking straps in use, prevent a pony resistance from escalating into a wreck. Equines usually give up fast if they can’t hoist their hind end.
A good driving trainer is a good investment towards enjoying the pony in the future.