I just installed one in my Scamp13D.
Picked up power from the cabinet on the other side of the bulkhead.
Used putty tape for the seal.
Start the process by locating it using a close estimate, drill a small hole at the center then scribe the circle to cut the hole.
I installed the inside escutcheon with 3 screws and nuts all the way through the flange on the roof ( half of them) the other three are attached only to the roof itself.
Finally... I trimmed the putty on the outside and finished the edge with black OMGSilicone!