Originally Posted by Goodbye13lueSky
also, how do you post at a canter?
Same way you post at the trot. It will feel weird to you but I assure you that it works for bringing that leg back. It also keeps you from slamming on their backs which will encourage them to stretch down, come underneath themselves and lighten up in the back. I have to do this with the nervous nelly TB that I ride because when he gets in this tense, stiff mode I have a hard time relaxing too!
If you are looking for mental images, the one that works for me is from centered riding. Picture yourself as a bottom-heavy doll, the kind that never really falls over when you push it. (I wonder if they still make those?) She also says to imagine your legs as roots of a tree and your body from the hip up is the trunk and branches. Grow up as much as you grow down.
Mieventer may be on to something though..... I'm not very knowledgeable with saddle fitting.