hairball,
I ran my astroplane using a fiberglass mast for over three years with perfect performance.
yes, the "mast" needs to be there, but if you use a non-conductive material for the mast then the antenna uses the coax shield as that counterpoise.
it really only needs metal down to about 9 feet below the hoop and really doesn't care what you use below that.
my plan was to isolate the antenna up in the air as much as i could, so i used a fiberglass telescoping mast, and choked the coax 9 feet below the hoop to stop the common mode currents at that point.
it worked amazingly.
one thing i must point out though!
if you or anyone else chooses to do the install this way, you MUST!!! use a proper lightning arrestor at ground level, with at least one 8 foot ground rod, right outside your shack in order to dissipate any static that can and will build up on the antenna.
if you don't, you have just created a big lightning rod that will shock you when the static builds up on the antenna.
I wouldn't take much stock in whatever those guys are saying, as they don't seem to have much science in their thinking.
LC