my 2 cents for what its worth...
Your tires look very similar to the Ventus V12's I was running. The V12's while great street tires, and not great on the track. Probably similar with the Super Sports
You may have the tire pressures off a little
I posted a thread with a good formula to calculate tire pressure for a balanced car.
http://986forum.com/forums/performance-technical-chat/58787-weight-front-rear.html
I have also found that at the track the tires heat up pretty fast and get very hot and had to drop pressure a bit. That was before I had the formula and I started off at 30/36. I calculated 32 f and 34 r for the tires I have now 225/45-17 and 255/40-17
For the stock sizes it give you 32 front and 31.4 rear on 17's 204/255 f/r! On stock 18" 225 / 265 its 32 front and 33 rear.
Those are cold pressure, so once they get hot, you will probably need to bleed them a bit
As Porsche with the factory pressures builds in understeer, going with the calculated pressure, the car is more neutral. I would imagine with extra understeer, the tires will heat up more as you are pushing them in the corners