This fan is great, pushes a lot of air.  It also fits quite nicely in the standard 14x14 rv roof vents if you are so inclined to try it out.  Take off the garnish, hold it in place with bungee cords, and seal edges with dish towels.  Now it's not the fanciest get up, but it does work, provides access to the on/off speed knob, and you can flip it.  My only complaint, like many RV specific products, is the price.