We removed the Fantastic Fans and replaced with the new MaxxAir Fans. It's the same type of fan, but, with a built-in cover that folds more flush with the top of the trailer. When open it provides it's own rain shelter. They were very easy to install, and fit the standard opening. The only glitch is the one for the bathroom because it's on the curve of the roof...it is a bit more difficult to open because of the resistance created when the frame tweaked across the curve of the roof.
Weather permitting, we open the front window and use the fan in the bedroom to draw the air through the trailer. This only works if the air outside the window is comfortably cool.
Also, the fans work great when cooking since they move large volumes of air very quickly. Just remember to open a window when using the fan.
These fans will work to move air in or out, as well as thermostat control.