I built up the area with some flox and glass, then drilled and installed with a touch of epoxy some brass threaded inserts from the hardware store. Then simply screwed in the light with some 440 stainless screws. I made the wires long enough and with a disconnect that I can pull them out with the light and then unplug them.
I came out rear spar near the bottom hinge pivot point and simply dropped the cable into the open bottom of the fiberglass fairing.