Bosan, is the maxxair the smaller one that goes over the standard vent cover? If so, I'd agree it's going to cut down on the airflow considerably. There are covers many of us use that are made for high flow fans. I think MaxxAir makes one but I'm not sure. We have the high flow cover over our FF because we want to use it rain or shine. It does reduce volume slightly but there is still plenty enough for us. This might be an option for you.
on edit -- this is the cover we have. It is a maxxair. The url at camping world is
http://www.campingworld.com/browse/s...13655&src=SRQB
