[QUOTE=kupeski;8789374]
This is really good for me, you’re making me think about my riding and how I ride 
As you can see in the initial video, he likes to anticipate the canter, so maybe I’m holding him back so he listens? He’s also not very straight moving- some people think since he was a driving horse, he’s used to shafts holding him in place. At the same time, he doesn’t always listen to my leg aid if both legs are on- for a long time I had to hold a leg off his side, to open the door for him to step over if asking for any sort of leg yield. He needs a lot of correction to do a straight line, which have gotten 100% better since I bought him. Anyways, I feel that on top of inside leg, I have to pick up the inside rein to catch him when he tries to dive in the middle (doing a whole 20m circle is really hard, according to Chubs).[/QUOTE]
Yes, sounds like he has basic problems with balance and straightness.
In the absence of any good coaching, you might want to look up “straightness training” online. There’s someone with a whole package of dvds and advice out there. I haven’t used her stuff, but it seems to be in line with what my own coach has had me doing over the years for these problems in my own horse.
That would be starting with in hand work, lateral poll flexions and lateral work, shoulder in on the ground, getting the horse to mouth the bit, reach for the bit, and also to move over and off your leg. Just trying to ride a horse straight won’t make a crooked horse straight. You need to stretch his hollow, stiff side, and also get him moving off one leg so you can nudge him over when he falls in or out. It sounds like you already do a bit of leg yield, but you want to work up to a shoulder in where he is moving correctly. Doing in-hand work until he has the balance, then doing it under saddle, where the two of you will have to also work on balance. At the walk, of course, at this stage and for a long time.
As far as falling into the circle, I’m unclear as to why you’d use the inside rein? Wouldn’t it primarily be the outside rein to keep him out on the circle?
I remember the one thing that was drilled into me in jumper lessons was to ride off the outside rein, and even throw away the inside rein. The horses would turn off the outside leg, the outside rein moderated the amount of turn, and too much inside rein just pulled them off balance. This took me a long time to believe, and get over the habit of hauling around corners with the inside rein!
Now that I’m schooling dressage, it’s still true. At this point, mare’s directional changes are really all off me looking in the direction, using my outside thigh, and enough outside rein to keep her from doing a small fast Western turn. Unless of course she is naughty and runs off course, then she gets some no-nonsense inside rein! But in the general run of things, I use the reins to tell her things about balance, bend and head position, not direction. If I do make the mistake of trying to turn her primarily with the inside rein, she gets very upset. And hanging on the inside rein on a 20 metre canter circle really messes up our canter. I try to let go a bit, and if she is falling in or taking off, ride off the outside rein with half-halts, and a bit of bend with the inside rein. But bend is touch and give, not a strong pull.
Also, as far as falling into the circle at the canter, you also want to do a bit of diagnosing. Is it worse in one direction than the other? And what is happening when he falls in? Is his shoulder falling in? Or his hind end? My mare has a tendency to fall in with her haunches going canter one direction, so she is basically doing a travers, which makes it easy for her to go sideways into the middle. But I think that at the trot, in the past it felt more like she was falling in with her shoulder, particularly in the other direction. Depending on what part of him is falling in, you would use different cues.
Also, you can’t get a good canter if you don’t have a good trot. Pony is inverted, upside down, not using his hind end, at both trot and canter. He doesn’t just fall apart at canter, it’s that it’s more noticeable there as he is going faster and you are less secure in your seat.
It’s true that a harness horse probably skipped a lot of basic work needed to make a riding horse, and that your boy is a bit older. But there are still a lot of things you can do to get him to carry himself correctly. I think that if you go back to basics with a good instructor, you will see a lot of improvement in everything within a year.
Maybe look at the straightness training website, and then see if there are any instructors locally that do that kind of work. Lots of people do this kind of work under different names, so they don’t need to be affiliated with that trainer, but rather to be doing that general kind of work. I wouldn’t suggest at this point you just buying a bunch of CDs and trying it on your own, as there is a lot of finesse and feel that can really only be taught in person.
