I was just finishing up the wiring for the rig and thought I would try to ground the frame for safety (shock hazard). However, to my surprise some of the members on my frame did not have a path to ground. The aluminum is annodized and that layer is a good insulator. If your frame nuts don't penetrate this layer there won't be a path to ground. I reccommend checking the resistance to all your frame members. Either find a spot to poke through the finish layer or touch your probe to the cut end. Also, you should check the actual resistance to make sure it is a good connection... don't just use the short/open probe as this can be a little deceptive if you have a weak connection.