On the cord cover idea, get a piece of hard vinyl / plastic. Cut it circular with the diameter to fit the "port hole" in the trailer wall (ie. slightly smaller than the existing cover) along with cutting the slot that is the same as the existing door. Use a stainless steel screw and attach the "new cover" to the back of the existing cover in the "exact center" of the existing cover ensuring that the existing cover still closes properly. Then, when you want to close the "opening slot", just spin the inside "cover" so that the two slots don't align. Reverse, to allow use of the cord in the future. A dremel or equivalent with bit can readily cut a plastic material disc.