Thanks for discussing my car guys, but to be honest: said setup was just my carpet setup - as mes mentioned - and OF COURSE did not work on clay. I did not even try to make it a proper one, it was just in a rush to have one more car around than my 4wd.
If I ever make my RB5 run on clay, I will get back to your setup suggestions (probably with rear end v3.0 and front end 1.9 beta RC2
)