Verdict is in: This HALO design is not ground dependent and can be mounted atop a section of PVC. See comments!
The gamma section isn't really a true gamma section. I found that
if I feed the center of one of the 1/4 wave elements the antenna matched
up pretty well. I ended
up tuning this antenna for the FM portion of 2-meter band, trimming
the elements to around 19 1/2" on each side of the Halo. Surprisingly,
this antenna works well
for FM, even if it is a horizontal design. What I like
most is that it's low profile, so it doesn't smack the tree branches when
mounted on top of my van. A plus!
Some comments about the 2-meter HALO antenna.
Christopher KD7REM mounted a HALO on his 1955 Chevy Pickup.
The STEALTH HALO images! (a small joke...)