The only way to truly tell if a western saddle fits is to put it on the horse w/o a pad - do not cinch up - & run your hand from the front of the tree (keep in mind the tree is HIGH - like where that front concho is - feeling under the skirts will tell you nothing). Run your hand from the front to the back - you should have even contact the whole length - not tight, then loose, then tight or any other combination - steady, even contact is perfect. If you have tightness by that front concho, too tight there. If gaps along the spine/back, then it is bridging - NOT good. Too tight at back will put pressure there too.
I hope that helps!