[quote="Jubilee Rose"]JDI, thanks for the critique. I do think maybe my stirrups are too long. It's weird because on the horse I used to ride I didn't seem to have this "chair seat" problem. Quote]
Saddle fit on a different horse can affect this. If you have photos of you on the other horse have a look and see if the saddle looks different. My saddle is hopeless on my older gelding, I can hardly do a rising trot the balance is that bad, but on my 2yo its fine.