I think when you set it up, before drilling mounting holes in your brackets, you should make sure the front & rear mounting holes are on a level plane. (equidistant from floor if you have a level floor) This will ensure the front & rear pivot points of the rotisserie are on a level plane and won't bind while turning, and will also assist in load balancing so that the car is less likely to spin on its own due to weight imbalance. (floor/frame of the car is heavier than the roof)

Tav