[kyngfish]

I might suggest something a bit simpler? instead of rails, why not something that has hooks on all four corners and you just hook it up to suspend under the car? That way you don't have to set up any hardware on the car.

Obviously something flexible or foldable would be best but I don't know anything about the kind of heat generated under those things and whether cardboard would create a fire hazard.

I would go through the garage and point out any other parking spots with fluid stains on them.