I thought about this, but in my car the roof colour does not contribute to the cabin temperature. I think this because, if I place my hand on the headliner I do not feel any heat radiating. If you have a bare metal headliner or very little insulation it would be helpfull.
In my car, the huge windows allow sunlight to heat the car. Here is what I would like to do. I want to use the perforated vinyl, printed black. I don`t think the absorption of heat will offset the cooling effect of shade. I will also do the rear window and 6 inches on the top of the windshield. or perhaps right down to the wiper lines.
