It is not the RADIO ground that was needed, it was the GROUND PLANE that is
needed on a 1/4 wave antenna.

http://www.eecs.wsu.edu/~pedrow/classes/ee416/Spring_2004/share_pdfs/teals/April_4/Quarterwavemonopoles1.pdf#search='quarter%20dipole '

You must have the outer conductor of the coaxial cable connected either to a
lot of metal at more or less 90 degrees to the vertical, or you have to get
scientific with 3 or more tuned stubs. This has little to do with the
radio's electrical ground. The link explains what's going on pretty well.

You should be ok with an aluminum RV as long as the coax outer conductor to
the skin reads a short on an ohmmeter.



Both radios are mounted to aluminum rails bolted to fuselage longerons
however each radio has an aditional grounding wire (from it's main
plug) to fuselage as a precaution. The SWRs also check out the same as
you discribe as does the performance.

Jim