I agree with partialtogray in the previous response. You need to go back and teach the horse how to use himself off the barrels. He is diving on his front end and doing what I call a wheelbarrow turn, no bit will fix it.
If his headset is naturally high tying his head down is a disservice, if his head is high due to trying to avoid the bit, a different bit will not fix that either.
Go back and work on exercises to increase his balance. I love serpentines, spirals, counter bending, half halts, roll backs, and lots of transitions all the things he needs to be able to do when going ninety to nothing around the barrels.