Installing the Maxtenna on the M5 is simple, but does require a slight modification to the existing GPS bracket.
1. Start by unscrewing the original M5 antenna from the M5.
2. The GPS antenna bracket that the M5 ships with attaches to the GCU at three points. You will need to remove the bracket by clipping those plastic stems. You can use a set of wire clippers (or a similar tool).
3. Once you have cut off the existing stand, you can thread the Maxtenna onto the brass threads you exposed when removing the original antenna.