I have always seen the trot leg yield done at sitting trot. However, if horse/rider aren't ready to do sitting trot well, can posting trot be used?
It helps if you post with the diagonal that will best help you time your legs aids. As most people tend to favour tapping with their leg as they go DOWN in the post, as as you want to use your leg to cue your horse's hind leg to step up and under, it can make the leg yield easier if you post so that you are going down in your post as the leg you want to cue over is coming up and under.
Example, when posting from quarter line to the wall, it is easiest to time the leg aids if you swap diagonals and post with the inside leg, this will time your going down in the post with the inside hind leg coming up and under, allowing you to better be able to time your leg aids to effectively cue the horse.
When leg yielding away from the wall, you can keep your post with the outside leg to effectively cue your horse.
Had a clinic with Tom Poulin this spring and we worked on just that (since my horse was completely tight and in full blown spaz). He stressed to rise over the outside shoulder. I agree to change diagonal so you can apply your inside leg easier, but for those capable of applying a leg while rising, this isn't necessary.
Thank you for posting that. It really clarified what people were talking about re: why it's helpful to post on the wrong diagonal when doing leg yielding. I will definitely try that. I wasn't getting much success in getting the horse I ride to "cross over"--probably because my leg was ineffective since I was using it on the "up" beat.
I saw the angel in the marble and I set him free. - Michaelangelo