The doors are somewhat controversial, but after testing mine last week at Elmo i am happy with the functionality and the dual positives. The drag reduction and also additional drag/stabilization when open. It is very interesting to look at the dust change when the doors open. If you go to John Wylie's videos form the May event, my car runs at around the 6:20 mark in the Sat #2 video watch the dust coming off the car at the end of the pass when the doors open. When I open them they only open enough initially for the chutes to deploy, not much differnt aero vs a car with no doors at that point. Its a significant change in the dust.