Lots of good info here, and not a single crack about all this talk of rigidity LOL!! Well done!
!
It seems pretty clear to me that if you want to track the car, a coupe is likely the best bet, as roadsters would not meet the safety requirements for most events.
However if you don't want to track the car, you have a lot more options. You can choose between the appeal of open top motoring and the relative style attributes of the coupe and roadster. I have been very honest when I say I really like both cars but owing to not being a member of the "One Percent", I had to choose.
Cheers!