I am not just so sure what type of fan to put for the back exhaust. My set up is this; my chassis is the Phanteks P400 and I have two 140mm air flow fans at the top, two 120 static pressure at the top and a regular 120mm fan at the back. My heatsink is the Cooler Master Hyper 212x. So My question is, should I use a static pressure or an air flow fan at the back because there is that space between the back exhaust and the heatsink that I'm not quite sure if it is restricting or not? The fan on the heatsink itself is facing forward, not facing the back side of the case.