For what it is worth, I'm using the carbon as my ground plane.

I've been on a couple of cross country flights and the only thing ATC is having trouble with is the noise in the cockpit.   I suspect interior and such will absorb some of that noise when I get to it.  Otherwise they are getting 5x5 on the signal quality (or at least that is what they are telling me when I ask).

Both the TXPDR and communications seem (thus far) pretty clear trouble free.  I decided not to put on an additional ground plane because the resistance of the carbon, while worse than copper or aluminum, is still pretty decent.  I took a chance and it seems to be working out so far.

Perhaps at some point I'll be proven wrong, but I think it is worth discussing and trying to quantify.  Kevin
N969RJ (flying)