I can't remember who it was made by(I will find out) but I used some insulation boards a few weeks ago that were far more sturdy than anything I've used before. It would be worth a phone call to the manufacturer to ask their opinion. I know cars are heavy but the weight is spread over four points of contact, each point approximately 25-30" square. I think it might work. You could always stick a couple of boards down,tile them and drive over them, park on them overnight etc.