yea, I cannot imagine an open top car needing more than 2 mirrors since turning almost any angle will result in nearly zero blind spots. Its one of the few cars I could honestly see you getting away with just one mirror if it were legal.
In normal driving with a human passenger it is not an issue. If my wife is not occupying the seat then my K9 co-pilot is there. She (the K9) likes to ride with her snout just on the outside of the wind screen, completely blocking the right mirror. A center mirror would give me the field of view to change lanes without having to turn and look over my shoulder
