After two failed wiring configurations, I found I should have done this the way I wanted to in the first place. No need for the fake bulb wiring adapter. Just drill a hole in the lens so the wires come out below the deck and solder the wires directly to the metal bits in the lens assembly...
I have a free triple yellow GT spoiler available but, of course, there's a catch. I'm looking to do a trunk swap with another triple yellow with spoiler delete. Let me know if you're interested!