I would like to get a growlab 120 which is 3'11''x3'11''x6'7''. I want to use a 600 watt air-cooled light. I was having trouble figuering what size fan and filter I needed for this size tent. I think I got it,what I got was 50.4 cfm.Can someone tell is this right.THANK YOU for any help. I used the formula in ventalation part 1.