I back-drilled the two antennna back-plates to the fuselage skin, using 11 additional holes on each plate for attach rivets, and four holes for the #8 screws that actually attach the antennas. I also marked, drilled and countersunk the plates for four nutplates each. Next, I masked and stripped contact patches inside the fuselage skin for to provide a good grounding surface, using a sanding disc to remove the paint. The attach holes in the skin were dimpled with a pop-rivet dimple set. The stripped patches and the backplates were alodined with a Touch-N-Prep pen, then I riveted on the nutplates.
All that remains is to rivet the plates to the skin, and the comm antennas will be ready to install when the time comes.
Masking the inside of the fuselage before removing paint.
Alodined back-plates with nutplates installed.
Backplate clecoed in fuselage, ready for riveting.