Sir Cranky is correct. Though I am now an inactive member of Club Cranky, I still managed to make two open track events this year, both at Pocono. PDA gave me no troubles whatsoever about only having one roll bar. The only down side is that I am not allowed to carry an instructor. What I would recommend is riding shotgun in an instructors car first, then when you run, the instructor will follow you. I rode shotgun in an instructors car, and it was a terrific learning tool. I could concentrate fully on the line he was taking and what he was doing.
Like he said, cars rarely wind up on their roof. I have only seen it once, and that was done by an early 20's kid with a brand new BMW M3 (less than 500 miles on it), who had NO experience at all. Thought he was playing 2Fast 2Furious and got in way over his head. The instructors basically threw out his buddies too, who all left with tail tucked between their legs.
If you drive with your head instead of your balls, it'll be the most fun you ever have with the Cobra. Hope to see you out there (and me too for that matter
)
Steve