What bit should I be using on my horse?

I have a WB x Welsh jumper pony. He goes fine at the walk and trot on the flat in a simple rubber racing Dee ring snaffle, I can even canter him on the flat in that most of the time. But once he starts jumping, he gets REALLY excited and takes off after the fences, I know this problem isn't all in fault of the bit, but he is used to having a close contact and tight rein so when I pull asking him to stop it doesn't do much, he runs through the bit. I am doing exercises to slow him down without changing his bit, (trotting fences and halting after) but he does just take the bit and run, so I am looking to put him in something a little (or a lot) harsher so I can regain control after the fence quicker, he is fine with single fences, but I need to have him collected enough to do a whole course, and with him taking off after the jumps I am having a hard time. I was thinking about a Kimberwicke or a Pelham, ( he used to be ridden in a pelham) please don't give me advice on how to slow him down, just on what bit would be a good decision for me. Thanks