Attached is a photo from the inside of my PH1 bootlid showing the slot cut for the standard reverse/reg plate light. It seems way too big and certainly needs a rubber gasket.
Is the slot too big or should there be a backing piece for the Lucas L469 lamp?
Take another look at the lamp. I believe the guys at the factory split the lamp and captured the rear skin as the primary mounting method, ignoring the two mounting lugs. Not sure about the gasket, but agree one is needed.