With new Fan-Tastic fans installed in 2 out of 3 of my 14" roof vents, I decided to get creative with the third opening.
Starting in either 1957 or 1958, Airstream offered an extra large unpowered roof vent called an "Astradome." It was the standard 14" wide, but 25" long. It's a neat 50s Airstream feature that I decided to add to my trailer.
The hardware is all the same as a standard 14" square opening, so all I needed to do was stretch the opening and mount a reproduction lid. The only thing left undone is to make a long screen for it.
Now my living room area will have a large opening in the ceiling and my galley and rear bedroom will have powered fans.