I already have 400lbs front springs. With Tarret bars, at least, it's not enough. I had the front Tarret full stiff, and the rear barely 1/2 stiff, with an LSD, and I'm still fighting a bit of oversteer(would be perfect for RA-1's, but not so good for R-888's - rear tire pressures are consistantly 2 lbs+ higher than the fronts -esp the out side rear). I will be trying higher rate front springs yet, and softening the front Tarret bar.

Springs are only one aspect of balance. Ride height and camber settings also play an important role.

Rear end high = oversteer.
Also not enough rear toe = oversteer underbraking on corner entry.

Eric I think 400# is the max spring for our Koni's ...

Right. 400's can work with our Koni's. 500s have been tried and don't. 450's may or may not.