If one looks closely in the picture there is a screw directly adjacent to the unit at the pivot point. There are actually three stainelss screws pulling the backing plate located on the underside of the bunker seat lid, in a triangular formation. The backing plate, made out of AZEEK board, was custom fitted and using some 5200, cemented in place. In the center of the screw head triangle, the half inch brass cup was inserted and set deep enough to being close to flush.
The idea of a safety lanyard is excellent, even though when the unit is plugged into the socket there is a screw cap to stop it from coming out. I will come up with a solution as a secondary safety strap. Thanks for that onecoolair.