Howdy. I had an amp installed a while ago, and am just tired of the engine whine. I'm also getting distortion or interference from either the brake lights or the wiring. The guy who installed said he tried multiple locations for the ground, and settled on the one in the attached picture. It doesn't appear that the paint has been sanded off, maybe scuffed a little. If I completely removed the paint, would this even be a good spot to use?