I added some suede to the inside of my galco king tuck, more for a little friction to help keep it in place, but it is comfy. I would think lambs wool would get hot in the summer. I would recommend memory foam. I used it once on a rig for my 1911 and it smushes down nicely so it isn't bulky, relatively cool, and very comfy. You can either get a bunch of samples from the tempurpedic folks or buy one of those bed covers they have at walmart for $40 and then just glue it to the back with 3M automotive upholstery adhesive. If you do that, it won't go anywhere, I promise you (I'm a car guy, I've used it a lot).
Good luck.

