I actually never got around to installing the 4F RS6 calipers. I used to have an old RS6 rotor, but Im not sure where it is now. If I were to look into it now, I would probably mount up the RS6 calipers with the stock S6 rotors, and see if the offset worked. There was only 5mm total diameter difference in the rotor (385mm vs 390) so the calipers should be able to accomodate the S6 rotors, if the offset matched.
If not, I would look around to see if any other rotors worked. There were some 400mm wave rotors that looked like they might work. Or, go custom.
I had the brake booster and master cylinder from a 4F RS6 at one point. It is at my friends shop, so should still have it.
The RS6 calipers are essentially the same design as the Brembo GT 6pots, btw. The Audi Brembo RS6 calipers have a bolt on brace accross the top, as opposed to the GT calipers that have the integrated.
If anyone wants the RS6 calipers, they are for sale. PM me if interested.
Just got the car back from tuning, and it is running INCREDIBLE !!!
Hope to get an update on the project thread up soon
Stay tuned