I'm hoping for some advice from more experienced instructors for riders who are stuck in a "chair seat" position. I'm an instructor-in-training, and am also discussing my problem with my mentor, but thought it wouldn't hurt to get advice/tips from others.
I have one rider who seems to be stuck in the most extreme chair seat position I've seen- as in, his legs are so straight, they're poking ahead of the horse's shoulders. I've had him in both an AP and dressage saddle, and varied the stirrup length to see if those things would help. I have also switched horses, as the first horse he was riding has a fairly bouncy trot, and that wasn't helping. Looking back, I think the chair seat developed in response to the bouncy trot, but now it's firmly cemented at the walk and trot.
In his first few lessons, he actually had a fairly strong 2-point position, and could really get his legs underneath him. But I'm very frustrated (mostly with myself) because I see him going in the wrong direction, and now 2-point is becoming difficult for him because his legs are shoved so far forward-which obviously makes it impossible to get up out of the saddle.
I've tried as many verbal explanations as I can think of. I've tried having sidewalkers help relax his leg back into position with a little ankle support. The only thing that has helped a little is having him ride stirrupless- that's the best leg position I've seen on him recently, but he is a little unbalanced (tends to list to the side) so I worry about riding stirrupless with him too long, and he is not ready to trot without stirrups.
He does not have physical limitations that would have him riding in this position.
I know you all don't have a visual on what he looks like when he rides, and haven't seen the interventions I've tried. But, can you think of any strategies that I might try to help him get in a better seated position?