The fans are much more substantial than a vent cover.I have already lost a plastic cover for the vent on the roof. Replaced with the motel one. Im afraid the fans will fly away. We drive 80-90 on the highway around here.....
I agree with the charger/inverter idea, adding solar charging later.
They will actually close themselves when the wind or rain becomes too strong.
Theyre bolted down with 16 1.5inch screws. Plenty are sold to camper trailer owners in Florida where they do travel at 70-80mph... (the benefits of cheap gas, I guess (we pay $7.25/gal here))