Rusty's previous owner was into the peanut roller business and taught Rusty to drop his head, so much that he became heavy on the forehand. In Rusty's four months, he's made a lot of progress to where he is really using his hind end at the trot, and his headset at the walk is great, and his trot has really come along. At the canter, though, we just can't seem to get it. Rusty leans on the bit terribly, to the point where I must set my hands on his neck momentarily to get enough strength to get them back in the proper position. I don't want to completely drop him though because he is also rather hardmouthed and doesn't stop easily. Sometimes, I really have to pull him back for quite a few strides to get him to come down. If I let him have his head, he gets all strung out and fast. I'm afraid he'll trip himself. I know a lot of things take time and practice, but I'm starting to dread riding him because it takes so much energy and it isn't fun. I've always thought of cantering as an exhilarating gait, but with Rusty, I seem to become horribly winded after two or so laps around the small arena (although I'm not in the greatest shape). When he really gets heavy, my instructor tells me to "pop" him with my inside rein and release right away. Lately, we've also been circling when he gets really bad, but that doesn't seem to work out so well as he always breaks into a trot and won't pick up a canter on a circle (I don't think he has enough balance). I am also instructed to hold my hands high when we canter but to not hold him in a frame (we've been working on framework at the trot). I can't ever seem to keep my hands up though because he literally pulls me down.
I guess I'm looking for exercises and just plain advice regarding this situation. If Rusty and I can overcome this, I think he has potential in the show ring. He loves to jump and has great distances even with his strung out canter. But I want to know if Rusty will always have this problem and how long it will take to correct it to at least the point where this isn't always blocking out way. Rusty is very intelligent yet stubborn, and I love him very much, but I want him to be suited to his job and for me to enjoy mine.
Also...I ride him in a dee ring snaffle and a plain cavesson. He wears a breastplate and a riser pad because his saddle always slides back.
Any suggestions or ideas are appreciated!