Hi,
yes I've tried the Composit. It is rock hard, just a shell covered with leather. If you can take that - I only tried it for 40 K, on loan from a friend. My Sitbones got numb as well. I wouldn't mind trying it longer. He says he rides 200K on this no problem.
I've now adjusted the Glider a bit and for 40 K, it just does not exist - wonder about how 100 would feel.