I have a chassis with two front intake fans. I'm looking to add 2 more fans, one in the rear and one at the top of the case. But to maintain positive pressure I think I need one to be another intake, and the other as an exhaust. I was thinking of making the rear the intake, and the top one as the exhaust. Check the diagram I made on my case. Does this airflow model exist? Is it acceptable in any way?