Thanks for the info on this. The reason I ask is that on one of the MHs I'm looking at, there isn't much space up top, and a vent cover is may not be a possibility, especially if I want to install a solar array that will be of any meaningful benefit, due to the shade caused by a vent cover.
Since the MH already comes with a lower tier Fantastic Fan, I might as well upgrade it to a 6000 model that has a thermostat and rain sensor. This will keep things in the rig from overheating too much when Texas starts getting the 110 degree temperatures come June.
