Talk to Skinner about bias control, as he has a mid mounted bias valve in his setup on the stock master cylinder IIRC. Not sure how effective the range of adjustment will be with GTI-R fronts, but I am sure he'll be able to fill you in. We have dual m/s sized specifically for the GTI-R fronts and disc rears with dash control, so it's a little different but having full control was something I considered to be a necessity on a track car to cater for all the different scenarios on the fly.
Tires tell you a LOT about what the car is doing that's for sure 
Personally I can't stress enough on how much the rear end on the K11 needs to be worked on. Very few people here push the K11 that hard or have much in the way of case history relating to handling improvements.....for the majority it's form over function and mainly about getting that low look
What setting do you run the rear ARB on now? One thing I was actually thinking of doing was to try a HD rear whiteline ARB and a standard front ARB, which may help to reduce some under steer but I realised i'd binned by OEM front ARB D'OH
