I agree with loosie - its on the shoulder because that's where you've literally put it. Bring it back so when the shoulder has full rotation/movement it doesn't touch the saddle at all. It shouldn't be on the shoulder full stop. I can't speak so much for Western saddles so someone can correct me if you're talking about the actual saddle itself or just the thick pad beneath? When younger I was also taught to saddle incorrectly and I'd mostly guess where it sits. Once I learned that the saddle should not interfere at all with their movement or joints it became easier to adjust with that in mind. Same as girths - they shouldn't be shoved right under the armpit (belly allowing ofc :P) The difference my mare moves when saddle is too forward with her shoulder jabbing into it and then when it sits correctly is night and day. She's way more willing, forward and doesn't trip so noticeably. It is strange to have the saddle so far back at first but only because everywhere I look everyone seems to have it too forward and is the norm. Just something to bear in mind. I am not a pro when it comes to saddle fitting but just wanted to chip that in. Good luck saddle hunting and adjusting is a pain!