Will be upgrading my panel to pretty much all glass in the following weeks, but would like to keep my 720. Will have a single Garmin GTN650 with a GNC255 NavCom., along with Aspen 2000 and AI CGR-30. Am considering installing an AirGizmo mount for my 720 but not sure if it will require an external antenna. Anyone mount one of these and willing to provide advice? Airplane is a Cherokee180C