I have about 5 feet of wire on the car end of my trailer wiring and keep it coiled up and stored inside the driver side tail light access. When I hook up the trailer, I simply hook it up and close the trunk lid on it. It's a good idea to put a plastic sheath over the wire where the trunk will close on it and make sure the wire isn't laying across the center where the trunk latch is. Also, have enough slack outside the car to allow for turning. I know this may sound a little unorthodox but it works well and I don't have to worry about damage to the wire connector from it hanging ouside the back of he car when it's not being used.

Jim