Do a little reading on ventilation. Nice attempt, and good start. The only problem is if you have one fan pulling air in and one pushing air out, it does the same thing as if you only hooked up one fan. For instance, if you had one fan pushing air out at 50 cubic feet per minuite, that means that 50 cubic feet of air is being removed every minuite. Likewise, if you turned that fan around, you would be pushing 50 cubic feet of air in every minuite. But it doesn't really matter which way you point it, either way only 50 feet of air are being moved. The same thing is happening to your cab now. 50 feet in and 50 feet out. If instead you hooked both of them up to pull air out, instead of 50 in and 50 out, you get 100 out. Make sense?