Eccentric bushes only is my understanding Serge, but I also hear that heaps of people cut and shorten upper arms to get camber (illegal).
No idea about the undertray, or if it was even there when I ran the car. MPC took care of the car as you know, maybe they have it because I know they needed to tidy up under the car quite a bit after we used it in 2008.
IMO, you're better off making an aluminium one that pushes snugly behind the lower lip, as the factory plastic one very quickly grinds the leading edge off on the road, and turns itself into a huge air scoop, and makes a horrendous flapping noise and bangs the whole car quite violently! First time it happened to us we stopped mid stage because we'd thought a wheel was loose in the wheel well!
The factory ones are far too expensive too, but I can assure you, I didn't steal it and take it home with me as carry on luggage
See what I mean? Rally Burnie, 2006;