A couple days ago I noticed patches just beneath my horses withers where the hair has been coming in with a sprinkling of white- which means something is not fitting right. I rode and while the rest of him was sweaty, those same spots were completely dry. I feel awful, because clearly the fit has been off for awhile (he's muscled up a lot since I got him) to the point that it has created those marks... I don't have a picture of him, but I have a picture and have made a mark of the part of the saddle that would be resting on that spot, so you have a clearer indication of what I'm talking about.
I realized it was too narrow, and could get an entire hand underneath, so I changed from a narrow gullet to a medium narrow and it was a little better but again, those spots were totally dry after our ride and I could fit 4 fingers under the pommel.
The saddle otherwise fits his back quite well and my trainer has checked and doesn't see a problem. Would an even wider gullet (I have the medium as well) make a difference? Or is it just the general saddle fit. And what happens to the damaged area, the hair will continue to come in white? Would it have damaged the ability to sweat normally?