Guido,
Like I originally posted, SL fitments are generally thought to be correct for our cars. Most also agree that the SL can accomodate slightly wider/lower offset wheels.
Anyway, if I remember correctly, you had 4 or 5 mm shaved off the mounting face of your rear wheels. That would effectively make the offset 29 or 30...and probably a much better fit.
If you have a chance, can you take a look under your car and measure the clearance between the wheel/tire and SLS strut? A picture would be worth a thousand words!
Thanks!