Fabricated cardboard-mounted template for locating holes in rib. Installed 4 nutplates (2 in each rib on either side of outboard bay). Etched ID info on retaining strips. Test-fit light mounting plate and verified best location of ballast unit (outboard of the bulb, with the wire harness protruding through the lightening hole in the outboard rib.) Drilled three mounting holes in mounting plate for ballast. Filed and sanded edges of mounting plate, retaining ring, and retaining strips. Primed mounting plate. Countersunk retaining strips.
I plan to leave the retaining ring natural aluminum, and paint the mounting plate and retaining strips with high-temperature enamel paint, baked in the oven at 250 degrees for a couple of hours.