A friend of mine has this very problem with her Walker gelding. He's short backed and has a lot of action in his back legs, so even with a short saddle and pad, he still rubs. She uses a Skito pad
with the real wool underside and a ThinLine pad
on top, to keep the saddle from making the rubbing worse. This combination has helped some.
Another idea would be to use a real sheepskin saddle pad right against his skin. If you buy a dog slicker brush and brush out the pad often, it will relatively clean. My daughter uses one under her English saddle and it's very nice. I wash it occasionally with a special sheepskin wash. You let it air dry, then fluff it back up with the slicker brush. I use a horse body brush to brush the dirt out between every ride. Sheepskin Saddle Pads - Square & Westen Pads - Western Pad - Arete Equestrian - Half Chaps, Skito & Supracor Saddle Pads... - (Powered by CubeCart)