I can add little in the way of intelligence to this discussion, but here was my experience:  I built my ES with a Lancair-supplied antenna in the vertical tail and I added a bent-whip external antenna in the belly just ahead of the front seat.  The belly antenna was bolted to a brass plate (I don't trust the electrical conductivity of an aluminum connection) with soldered-on copper ribbons radiating outward.  I connected this antenna to the #1 radio (Garmin 430) assuming it would give the better performance.  I had many complaints of poor reception.  Since there was a ground braid that went by the antenna I connected it to the brass plate - the reception was then normal.  However, I still have an occasional problem when operating in "poor coverage" areas, but can usually fix it by talking on the #2 radio, which is connected to the tail-mounted antenna.  So for me, the internal tail-mounted antenna has performed better than the external belly antenna, even with its "correctly done" ground plane.  However, it might be partly because of my "down and welded" landing gear that surrounds it.

Gary Casey

ES #157

 

From John: