hi, at shows does your pony actually properly work on the bit or does he just tuck his head in. Teach him how to work propery and bring his head in and hind quarters underneath him, there are a few training aids you can use to help do this like side reins and pessoa training aids while he is on the lunge. I taught my horse to go on the bit just riding him, mainly because he's a little ******* to lunge, I find this if more effective as they learn how you are asking them with your hands and legs and rather than just having their head reined in by side reins. I started by taking quite a firm contact on both reins and using my fingers to kind of niggle at his mouth like a half hatl kind of thing with one rein then the other, if you feel his mouth soften or his head drop then you relax your hands straight away and tell him good boy, subsequently they learn where your hand are soft (when their head is dropped) remember to keep your leg squeezed on all the time you are asking to push him forward so his quarters come underneath him, by taking a firm contact a pushing with the leg but not letting him get faster it makes his quarters come underneath him, he wil be working between your hand and leg, listening to you more and probably go alot better. This make take a while to perfect so he drops straight down, still lunge with side reins though as is helps them get used to having their head in that position and helps the muscle build up so it is easier for them to work properly. Also make sure his head never tucks in too far behind the vertical it should be straight and not tucked to his chest or he will not work properly, hope this helps!!