I ran the Petit Race this weekend. It was on a inndoor clay track with a very hard pacekd rough surface. This track:
http://www.youtube.com/watch?v=ScJF4QsD3uY
I started out with the basic setup, more or less. I have never raced on this layout, and never tried the XB4 on other than carpet. So never mind the end result
During the day I tried different setup changes, but before my last quialifier I changed diffs to 5K front and 2K rear.
This suddenly made the car a lot better. I thougt it was my damper setup messing with me, because the car was not handling the rough surface at all. But the diffs made all the difference.
I need to go back there to do more work on the car, but I was amazed at how much the diffs changed the handling...