Going to revive this tread a little.
I am at the point in the rear electrical that I want to add trailer electrical outlets to handle most trailers I plan to pull. The most common would be a tow dolly, rented, and I think most of those have the flat 4 pin connector. I want to wire up a combination 7,5,4 pin adapter to handle most of the options.
With that said, I have a concern. If there is live battery power, ground and connections to all of the lighting circuits, wouldn't someone be able to just jump several of the pins together and fry your bus electrical system? If so, how could you prevent that other than a locking cap which I have never seen?