well his feet have been bothering him too. He's had abcesses before and had to have surgery on them, so we want to make sure his feet are ok. And even though it could have just been a scare, we want to make sure. Gem has always been a little iffy with his back. I can't really explain how he would react, but it wasn't like he was grumpy about having a saddle on, more or less that he didn't want the weight of it on. He was even worse with a western saddle.
Another thing too, is that when I would sit or post to his trot, he'd have a somewhat choppy stride, but as soon as I went up into a half seat, his stride lengthen and he seemed to be happy not to have weight on his back.