Anyone who has an MBX6 knows there is not much room to mount anything on the radio box. What I have done is used velcro to mount it in front of the transponder and route the plug into the box through the grommet, so there is no drilling of holes. The wire is taut and the plug just sticks out enough to reach the battery lead.

I have 3 race days with it and it has worked perfect with no movement at all on the velcro.