I actually have 2 80mms in their special "slim" spots, the support bar and the other side, (mobo). i got a 37.44 CFM fan up front replacing the OEM 120mm fan that came with the case, and i got the silverstone 92mm in a 80mm frame Link: http://www.silverstonetek.com/products-fn82.htm in the back for exhaust.

both 80mms are blowing in, so would placing the OEM 120 in place of the duct on exhaust even it all out?