I don't know the specific answer for your situation, but the Glasair
III uses a carbon fiber horizontal stabilizer and they mount the
antenna right inside it. up against the carbon fiber lay-up.

Thanks, That answers my essential question and I can now position my nav
antenna. I'm familure with your G3 structure but didn't know that this was a
common place for an antenna. If it works in that application it should work in
mine.