I installed the Bob Archer COMM antenna for the Comm2 antenna as this is designed specifically for composite aircraft. The antenna installs on the inside of the fuselage right behind bulkhead A (immediately behind the baggage area). It forms nicely around the curvature of the interior fuselage and is held in by 6 blind rivets in the fiberglass wall.
I have not yet wired the antenna, but that will occur when I begin work on the panel.