The guys that do my suspension installation have installed springs as high as 1200 lbs on the rear of these GT2's and found that it's just too much for anything other than a Billiard table smooth surface... For Sears (especially) , Laguna and Thunderhill (my local tracks) a bit of compliance in the suspension is a good thing and helps deal with some of the ripples and bumps in the surface of the track.

Weight transfer is another issue. Sometimes, softer springs allow for more weight transfer to help with traction.... It's all a question of balance. At Laguna, I put an extra 50 psi in my remote shock reservoirs to help keep the rear from squatting as much on corner exit, as I was experiencing understeer coming out of turn 5 (an uphill turn).. the rear was weighted anyway because of the uphill attitude of the corner, then when I got hard on the power, the rear squatted and transferred even more weight to the rear, thereby unweighting the front which caused a lack of grip and therefore understeer. The extra resistance (effectively increasing the spring rate) at the rear helped cure that corner exit understeer.

 

OK a little OT here, but all for fun right! I know what you're saying about ripples and kerbs... I actually had a pretty decent setup even with the soft KW V3 for Turbo (softer than for GT2) just b/c it was compliant, especially works with lesser grip tires than R-comp (say a street performance tire). But got advice from a Porsche race-engineer back home to run 120-140 front and 160-180 rear depending on tire, which corresponds pretty much to 680 and 915 on the lower numbers... I went just a tad below with 12kg and 16kg to be on the softer side of that range, here in Socal and in Nevada there's always a little dustiness and usually very hot on track. I will definitely pay attention to how these springs may cause skipping over ripples and bumps, hopefully the shocks can handle it. On street on way home from shop I already felt a bit of wheels being airborne over some sections - however on sections where surface was decent it felt really amazing, chassis just held on. Very much look fwd to test it out on track!

 

Great pictures. I love that track. I've only been there once which was over 4 years ago. I had so much fun that day.