I did take some saddle fit pictures right after I got this saddle, everyone seemed to think it was fitting pretty well... But I have ridden in it significantly more now than I had then which could definitely have slightly changed the shape of the saddles padding...
I have to link to them because photobucket doesn't work on my computer, sorry!
Side view with a thick pad: Sta.sh
Side view with thinner, english pad: Sta.sh
Back view, with thin pad: Sta.sh
Wither shot, with thin pad: Sta.sh
I can say that the thicker pad made it fit terribly. Like, the saddle was sliding all over and it was just terrible. Also, I've never actually put the saddle on her, no pad... I really should do that. Maybe tomorrow if I have time. :)
I did ride in it with the baby pad today and my mare was definitely moving more freely than I've felt in a while (we've been going through ill fitting saddles, one after the other). The baby pad didn't slip much either. It did slide back slightly after some intense trot/cantering uphill for 10 minutes but I readjusted it and it stayed after that...
The dirt marks on the pad (it's white) were also very even everywhere under the saddle, anecdotal-y.
I would say that her back is still developing muscle. I mean, her back has increased in width and muscling dramatically over the last year and I'd assume that that trend is most likely continuing... And she is nearly 27 so she loses and gains muscle like crazy.
To Tinyliny's comment, I'm pretty sure I do grip with my knees. :/ At least, my lower leg moves a lot while I post and I've heard that that's a sign of knee gripping... Is there anything I can do to fix that?