I would then go with khuon's suggestion (post #6) using the skewer mount. They also have very nice 'P' clamps shown on that same webpage. Either mounting system should work well, but after seeing how nice their clamps are, I personally would go with the clamps. The skewer mount is a bit of a hassle when time comes to removing your rear wheel to fix a flat. I have a skewer mounted rack on my mountain bike frame.