ASW27 Trasponder Antenna Installation Inside Fuselage.

I am resurrecting this old post as some pilots I know are installing transponders this winter. The key questions are the location of the antenna and the type to use.

1) Does the blade type antenna provide "better" coverage than the rod type? What about aerodynamics between the two?

2) Potentially dumb question - Ground Planes - It was mentioned above by UH that the ground plane should be on the outside of a CF glider. As carbon blocks RF transmission is it considered conductive? If conductive, and grounded to the avionics, can the CF constitute a ground plane? I saw another RAS thread on this same subject without a clear consensus given.

Thanks, John