Have two fantastic fans, one in the bath, one over the bed. Both with smoke colored Max Air II covers. The covers prevent the fan from opening all the way, but they still move a lot of air.
We have the manual on/off, three speed, with the reverse switch. Most times we have one moving air in, while the other moves air out. Which one is reverse vs. forward depends on the orientation of the camper. We us the over the door clothes hanger brackets, from bed bath & beyond, for hanging wet coats on the inside of the bathroom door on hangers. To prevent the bathroom door from being sucked in by the fan, we just slide the bracket to the edge and it holds the door open ~6".
The fantastic fan also comes with other options you might consider. We have a double pane, smoked colored dome, on each, which seal well. Warmer during the winter, less condensation on the inside of the dome during spring and fall. Dark color makes it easier to sleep during the summer.
Max Air cover does a good job of keeping the rain out. They don't do as good a job of keeping out cold, blowing snow, if the dome is open.
'05 Ram 3500, 4x4, DRW, LB, 6spd man, CTD, PRXB exhaust brake, Roadmaster bar
'01 Corsair 10'8" - 4,200 lbs., Xantrex XADC 80A, Link 20, 4-Lifeline GPL-4CT, PowerGate Isolater, 2 AWG wire, PI 30A EMS, 2 Honda EU2000i, parallel kit, ext. duration tank.