I grounded mine behind the panel next to the glovebox and the doori figured it out. If you're experiencing problems its because you have a bad connection *somewhere*. I was frustrated because the new circuit I created, I'd tested prior to putting it in the car and I still had issues. In my case, there was nothing wrong with the new circuit I created. I made a bad assumption:
The recommendation is to take advantage of the screw underneath the glove box as a ground. There is a piece of plastic between the frame and the screw. I mistakenly thought that having my o-ring terminal in close contact with the screw head (which was therefor screwed into the frame) was a good enough ground- this was incorrect. When I put the o-ring terminal directly against the metal bar and screwed the plastic down over it, I had a good enough connection.