Good grounds are very important. Single point grounds have important applications in some electronic and electrical situations, but I'm not so sure that it matters in automotive DC applications. Personally, at most grouind connections, I bare the metal, then use star type lock washers on both sides of the connection. Also, in agreement with previous post, I would never use sheet metal or tapping screws for any electrical connection. I would use machine screws / bolts, with lock washers and nuts.
