Have you tried the Classic Equine ESP Contoured pad? We use it for our higher withered horses. It has memory foam on both sides, without building up the height of the wither. The memory foam really conforms to the horse and seems to really fit a lot of horses. They're really good quality pads that stand up to a ton of rides! The contoured shape also allows them to sit on a high-withered horse and still fit down on the back properly. I highly recommend trying one. I've never had any dry spots or rubbing with this pad.
until one has loved an animal, part of their soul remains unawakened