I had a set of frame sliders I tested a couple years ago and they did do very well. The bike didn't get scraped, but the aluminum slides bent and marred the frame. With my new bike i looked at a couple designs then decided to look at a set already made then make them better.
CDG had a set on his bike but they didn't look long enough and they had a metal insert. I wanted to get away from metal so that the sliders would bend a bit (or a lot) and the delrin would chip or deform to save the frame and hopefully keep the fairing intact. Second they had to be long enough to keep the engine case from touching in at least the first 50 feet or so. I put a board up to teh sliders after installation to make sure they were extended enough.
Oddly enough Delrin is not cheap and cannot just be ought anywhere. The grade I was looking for (100 durometer or "synthetic stone") was found in a $180 bar. I've made a couple for others and finally got some bolts to make my own (thanks Brad).
Made on a Cummins lathe. 7X10.
Pretty happy with the results: