Originally Posted by Chris Nicastro
The inlet area has to be equal to or greater than the FSA of the fan.
False. Inlet area can be as low as 65% FSA if the shape is just right. 80% is a reasonable number to shoot for, especially with new fans having more than 4 or 5 blades.
For the exhaust, make sure you're looking at half the area, not diameter. As long as the total area is equal or less than 100% fsa, I think it will work ok.