The supplated nut plate doesn't fit the Whelen Microburst II lights that I bought, so I fabricated new ones out of .02" thick aluminum sheet. I then marked holes on the wing tip and drilled them to the appropriate size.
My first attempt at installing the rivnuts didn't go so well as the rivnuts clinched under the plate to the fiberglass only. I subsequently had to drill them out and try again with only marginal success.
The problem is that the fiberglass area under the plate is not flat, so I had to tap the plates with a hammer to mold them to the shape of the underlying composite.