ya it would work, but find a better spot, on my car my grounds are to my trunk and to a bolt on my back seat, the roof would be a uh well werid stange place lol
He isnt talking about his system. He said for things like lights.... Yes as long as the amperage rating of the device is not too high you should be fine. Be very carefull though as you will have a SERIOUS rust problem if you do not properly seal it where you drill for the ground.