I have 32mm front and 25mm rear on the RS4. Like a go cart with Eibach springs as well but you do need to be aware that race cars have adjustable bars for a reason. Any rain, loose road surface or even in winter when the tyres and road surface are really cold and you risk just looping it on the street. Sort of makes you look a bit like a goose if it happens. Eibach recommend disconnecting the bars in the rain and the situation is not made any better with RS level springs to boot. So the stiffer the installation, the more restricted the car becomes in variable weather. I like the RS4 with my setup but as I have an almost bone stock RS6, I have a fall back for rougher roads or inclement weather.
TUNING YOUR EIBACH BARS
a)1sthole / Softest Setting.
•Reduces over-steer
•Use in rain or on slick roads.
•Use on rough or bumpy roads.
•Increases comfort.
b)2ndhole / Firmest Setting.
•Reduces under-steer
•Use on dry roads and tracks.
•Use on smooth roads and tracks.
•Do not use on wet or slick roads
C5 RS6: Sportec, Milltek & Wagner -- B5 RS4 : modified -- B5 Audi 1.8 quattro 132 Kw -- 2007 VW Touareg TDI 3.0 with air suspension and lockers-- UNIMOG 404 TLF8