OK...however ima only get one good fan with ni inatke fan..itll be passive intake..also,do I leave the edn of the far hood open..or close it somehow so only the hot air in the hoods gets cooled?and lest say i dot run it like this 2 keep the fan out of the way..O--------O-------##...can i still attch a carbo filter at the end..and will it be enough to keep both hoods cool..since it it is kinda far from the hoods themselkves??
Ok I think I know what You want to do.
I would set it up like this
HHHHH = Carbon filter.
HHHHH---------O--------------O-------------##
As OregonMeds said, You can always reduce the output with a "dimmer switch"/ rheostat type of device.
So depending on where You live and how warm the room gets, I would go with a ~500 CFM fan for the summer time. Plus once You add the carbon filter You knock down some CFMs. So a 500 CFM fan might only run at 420 CFM
after the filter is attached.
The thing about running it this way, with only one fan, is that the fan has to run all the time while lights are on, and You won't be able to control the temps as accuratly as having an independent exhaust fan controlled by a thermostat device.