Winter Car cover idea's ?

As far as laying a plastic on the ground, I like to start mine and run it until it's nice and hot, so i have no condensation in the exhaust.
Plastic underneath is not the best, I use a small fan (110v) under the car, hooked to a timer, it goes on and runs for 2 hours everyday, I find that to be sufficient to circulate the air and dry off moisture.

Giles