Ah, the butterfly snaffle.....an interesting bit, not one I would suggest but whatever. Anyway, are you planning on showing? If not, a simple o-ring snaffle would be fine. No reason why a snaffle wouldn't work. But if you want a curb bit I'd go with one that has a short shank and a low port. Look into the Myler bits. Those bits have independent movement on each side which is great. Also, with whatever you use, get a curb strap, not a chain, so that the bit doesn't slide through the horse's mouth.