I have ET15 which is fine with no rubbing at all (these are on the back as I have 7.5x16 ET20 at the front) I've got the front and back dropped about 40mm on Fk Highsports and all seems fine. Although the clearence for the front on full lock is about 3 or 4mm on the inner arch both ways. So about at close as it can get.
Hmm, now i just need to find a nice friendly english speaking garage in München (story of my life.... never going to find that it seems)