I have a similar problem with western saddles being uncomfortable. For me, it feels like my seat bones are teetering on the edges of a block of wood. My seat bones REALLY hurt after riding in a western saddle, and I've ridden in probably around 10 different ones. Honestly I think it might have to do with the shape of the tree. None of my friends have this problem, but I have very wide hips, and was wondering if my seat bones were just wider set than the average person? It's the only thing I can come up with. I never get that feeling in english saddles, and the only western saddle I've never experienced this in was one that was much too small for me (I think it was a 14 inch, and I was over flowing out with back :P).