Any downside to this?
As Tim said, the vibes can really do a number on electronics. My first couple tries my radio was loose in it's holder and the movement in the cradle and between the radio and battery pack eroded (ate) the battery terminals. I now use a couple business cards to make it tight and the problem is less, but I still see some erosion.
I'm using the brake reservoir clamp ball. You can see it easily here.
http://www.randols.net/Connie/ThrottleCables/cables_into_throttle.jpgNow I just throw it in the top of my stiff side tank bag.