As it's an open car, it'll have to adhere to the requirements for convertibles. The atom has a roll structure if I recall... The question is if a) it meets TTR requirements for roll bars, or b) if it is spelled out in the owners manual as -specifically- being there for rollover protection. If so, then it still needs to meet the height requirements. If the top of the drivers helmet is below the level of the bar, he's good to go.
-Josh2
Josh Hadler
CO Region Time Trials Chief Operating Steward
RMDiv TTPM
TTAC