The Sensation treeless saddles are lovely, but as the poster above suggested, some narrow horses with prominent withers are not great candidates for treeless. My horse, for example, even when in competition-condition, is more “triangle” than “U” shaped over the back, and the Sensation creator didn’t recommend her saddles for him.
I know you asked for Western, but I ride in a Wintec Isabelle, and I have the “English” saddle bags from Sungpax. Between my pommel and cantle bags, I can fit what I need for a full day’s ride, and I find the deep-ish seat and higher cantle very comfortable for long rides (8+ hours in the Rocky Mountains, 4-5 hour conditioning rides in the bush.)
There is a saddlery in Alberta that is very reasonable for custom Western saddles, and I intend to have them build one for my horse (after I’m done getting his made-to-order Jump saddle done :rolleyes:) they are called Ertman (780) 967-5103. I believe their base price is in the $2000 range, but so far, their saddles are the only Western saddles that I found as comfortable as my Dressage and Hunt saddles for trails. I find most Western saddles way too wide, hard, and they tend to tip me backward. The Ertman saddle I tried was really comfortable and put me in a secure-feeling position. They may have a tree that will work, although I’m not certain they will be able to work remotely. Worth a call, at any rate, as they may be able to tell you what type of tree will work for this horse (many Western saddles use a variety of “standard” trees, not dependent on brand.)