Pete,Let me throw this out there, please tell me if I'm in the ballpark.
I have Spax shocks and want to replace the stock springs.
I run the car normally with stock wheels, I have Proxes4s (245/50-16) on the rear and R1Rs (225/45-15) on the front. The fronts are stickier to mitigate understeer and I'm pretty happy with the balance.
There's way too much body roll with the current setup and I can't get the front down as low as I want. I do like the ride quality for normal street driving and want to avoid an overly harsh ride.
Next year I plan on tracking the car. I have a set of Ronal 17/18 wheels that I may put R-comps on for track days.
I'm thinking Eibach springs, 2.5" ID, 12"-275lb/in Front and 12"-300lb/in Rear. Does this sound about right?
I'm curious... how did it work for you? Any observations to share w/ us?