That's an e-z out there, mate.
I have the GTS concept '00 that I've been fooling with. Not a great tune yet, but I can finally win pretty easy at Indy.
It's a long, heavy way to fast to corner car and I think It has massive understeer/speed problems so this is what I did:
Bring the suspension settings back to default, slam the spoiler and the springs to the ground, and stiffen up the spring rate pretty tight, lower the anti roll bars accordingly. Obviously the hillier the track, the more clearance you need, but leave it as low as possible.
Then raise the rear about 5-10mm, tweak the camber to between 2 and 3 on front and rear. I just left the toe and dampers alone so far.
Finally, that car will go way faster than most, so slow the heck down for corners and use the full apex, It's not likely you can accellerate till you are almost straightened out.