Since mine is so tight with the additional wires, it doesn't move at all. Try it out and see if you get any movement or skipping. I doubt you will, but if you do, then add something to the back. You know, if you actually use that metal back-strap and someone tries to steal your radio, they probably won't get away with it. Of course, it is such a pain to install in the first place, that 99.98% of people never install it anyway.