Hi Barry

One problem with carbon is continuity between the fibers.  Even though the fibers are very conductive, the resin matrix is acting as an isolator.  I had asked the same thing of another engineer about using the carbon as a ground for the radios and that was his answer.  But it does beg the question about higher fiber content composites that are substantially debulked and have much higher contact area could be superior to it.  You would still have to figure a good reliable way to attach the ground but there are conductive adhesives that should work.