Dressage Legal bit for hard mouthed horse
First a brief history, my twelve year old QH was used as a western speed/rodeo horse before I got him. His past owners rode him in a twisted wire snaffle because he had "a tendency to run off." When I got him (three years ago now) I used a pelham bit on him. Worked really well, never had any running off issues, but his mouth is very hard.
Flash forward to about half a year ago, gave up on making him a jumper, and started working on dressage. Problem is, at intro and training level, pelhams are not allowed. Have tried him in o-ring/egg-butt/d-ring snaffles with no luck, half the time I might as well not have a bit in his mouth.
I do suppling and bending excercises until I am blue in the face, but he doesn't become any more responsive.
Any ideas on a good bit to try? I really am open to anything legal for my level.