Yes you can run the 0 g under the vehicle. It would be safer to run on the side of the vehilce panel. Running the wire under the car would need much more work. You can try adding some PVC pipe into the wire. and get some bracket to hold it. Wire loom will not be good to run under the car. If it your daily drive then i wouldn't put it.. If up to. It not hard to strip a an interior vehicle..