I've done mine in aluminum secured with camlocs for easy removal. One panel over the area where the axles go through, and one right in front to cover the two different angled tubes coming from the top and bottom. I also have one mocked up to go in front of the rear wheel up to the bodywork but I may not complete that since Fran hinted that the Aussie RCR dealer (sorry, can't think of your name off the top of my head) should be producing a nice option soon. He has posted a pic of it somewhere on the forum. As I have it mocked up, it is supported on the bottom by a "tray" coming out from the bottom tube that will also secure the bottom forward edge of the bodywork. Again, all secured with camlocs.
Also, there are various plastics that may be worth trying that would eliminate the pinging sound you'd get from flying rocks and may easily conform to odd bends with a heat gun. With the seemingly unlimited choices of plastics though, I just do not know enough about them to make the best decision in this area.