I have a model A tail light with a tag holder in the center of my hatch. Also will soon have two regular run/stop/turn LED tail lights. I want to wire the stop light in the center. My tow vehicles are already wired for a boat trailer typical 4 wire setup. How do you make the 3rd stop light work? I know Kai took apart an aftermarket 3rd stop light and took out the device that makes it work, can you buy those without buying the whole assembly? Lookin for "easy" answers.