Hey I'm lookin into some grow tent vents and want to know what i could get away with keepin the temps down. Size of Grow tent is 20" deep, 36" wide, and 64" tall. the fans i'm lookin at are the 4" inline fan/carbon filter combo (170cfm) and the 6" inline fan/charcoal filter combo(424cfm). this fan will be venting the tent(housing a 400w hps with forced air cooling)(6" inline duct fan for the reflector 250cfm). I will buy the 6" if the 4" inline won't work. Has anyone seen a simalar setup where this has worked with a 4" inline fan? because i don't want to buy it and it won't be suffice. if anyone could get back quickly on this one it would be more than appreciated. Thanks, LogHead