I have had 5 trailers with the Fantastic Fan and each time I have had to upgrade or modify the basic 3 speed to slow down or add a reverse, the low is too fast and you have to cut the speed in half. You also have to install covers to operate in the rain. That said, the MaxxFan I now own already has the cover and 14 speeds, no modifications are needed. You do the math.
never in doubt, often wrong