I use a Black Forest treeless on all of my horses- My Lusitano mare definitely has withers and it fits her fine with ample clearance. I use a Grandeur pad under the saddle and it has been fitted with lexan inserts- the pad and inserts really help distribute the weight and keep the saddle from resting on the spine and withers. My mare is trained through GP (although me not so much)- her movements feel fabulous in the treeless!!
“While the rest of the species is descended from apes, redheads are descended from cats.” Mark Twain