This is the absolute best way to do it. A nut, a bolt, a hole, and a sanded bare metal surface is what you need for a proper ground connection. Self-tapping screws will loosen up over time and cannot be relied on for holding down a ground terminal. It's easy and simple, but most certainly not the best or most reliable way to do it. I'd even add a lock washer or use a locking nut.I have basically done the same as Boats with the cars I previously owned. I would drill a hole and use a bolt. I would use a Dremel tool to sand the area and then paint over everything once it is secured to prevent rusting. The area where the spare tire is stored always seemed to work best for me.