Carl,
I would not back off too much on the front camber with the 275's. You may want to ask David Andrews what he's running alignment wise as he has about the most experience around running faster times on PS2's and Gen IV Vipers. Terry Rossi sets up his car.
Bruce,
I liked the way the Kumho's felt when they were new but they did wear out the outer shoulders of the rear tires pretty fast at Willow Springs, had to switch them on the rim after about 8 sessions, which is a pain. This was with 1.5 negative rear camber, stiff rear springs and Moton Shocks.
Fronts faired better in terms of even tire wear at 2.7 negative camber. Problem is the Kumhos are only available in 305 front and the car will push at speed as the front tires wear out, which happens pretty fast to these 305s.
Willow Springs is ******* tires.
The Hoosier R6s did wear better and felt a bit faster. I've gone back to 315 fronts / 345 rears with the R6's and think they're about as good a tire as you can currently get for a DOT track tire.
As mentioned above, the Dunlop race tires that you can sometimes get "used" from John Berget are the stickiest, best feeling tire I've run on Vipers. Get the harder compound though as even it wears out pretty fast, like one weekend at a slow track. At Willow Springs, they might not last a day.
Dan