[Perfectlap]

no you can run your car on just about any track with the hardtop. Presumably if you can fit in the car with your helmet on you are ok. Not everyone can do this though...like my friend who is 6'3 and simply can't fit in the car with a helmet on unless the top is removed. He would need a roll bar extension to run in my car on any track.

I don't think I have ever seen anyone administer a broom stick test at an autocross. THey probably should, I'm sure at least one big guy in an S2000 or Miata, Z4 etc has had the top of his helmet crest above the windshield header.