I found it easier and just as safe to run the wire under the car, keeping it inside the frame rails as much as possible for protection (the only thing that can hurt it is if an idiot doesn't line the jack up correctly). I then drilled a hole in the trunk floor and ran the wire through the hole. My ground is the frame rail under the trunk. Works very well and the lights were noticably brighter after the install...the factory battery was 2 years old at the time.
