What bit is suitable for my horse?

My horse was similar when I tried him in a Cheltenham gag - I've had him since November, but we're fairly in tune to each other. He is only just turned 6, and I ride him in a pelham cross country, as he gets extremely strong. I find he dislikes anything too much in his mouth, such as rollers, or waterford. Try a french link full cheek - I ride Crackle in that for dressage, and he seems to respect it, and it has quite good steering.