Go to the motorsports section and check out the 595RS race tires.
You have seen the May issue of Grassroots Motorsports??
The 595RS is also said to exhibit easy breakaway characteristics, a handy feature for those in the drift scene...
has alot of void area and quite a bit of flex in the sidewall, which made the tire feel pretty squishy and squirmy at the limit of adhesion
Sounds like a good drifting tire...(blech).
I certainly wouldn't swap out my RT-615s for the Federals for AutoCross/Road Race use.
BTW, the 595RS is no where near an R Compound tire...it's a street tire with a 180 TreadWear.