My lease-horse is using a Tom thumb bit (the american version of tom Thumb). Straight shanks and a single-jointed mouthpiece with curb-chain. As an engineer, I've been sitting with this thing at my coffee table trying to figure out the physics of it, and it seems like the worst possible design for a bit. Poor communication and harsh. Maybe I'm wrong. The horse direct-reins with this bit - I don't know how he does it. I don't want to ride with this bit, and the owner has given me the green light to use whatever bit I want.
2 pieces of information: I ride English - pleasure and trails only - no shows. His only vice is that at least once per ride, he spins around on a dime and bolts for the barn. He's easy enough to stop. I need to make sure that I can still stop him in the bit I end up using. He is very responsive to all cues.
I'm considering going to a low-port Kimberwick or a Baucher. The Kimberwick has a little leverage and curb action, which he's used to. It has some extra stopping power if I need it for the bolting. I can reduce the leverage if he turns out to do well in it.
The Baucher has the pressure on his poll that he's used to, while having the direct contact of a snaffle.
I prefer a simple snaffle. I've always used single-jointed loose-rings for starting horses, then french-link eggbutts for seasoned horses. I tried the French-link on him, and he hated it: fidget fidget tongue-lolling, gaping mule-face.
Any preferences on Baucher vs Kimberwick vs something better?