You make a good point, I do always see tents set up the way you say. On this grow I wanted to have 2 stage ventilation because I wanted the fan cooling the light to be completely separate from the fan blowing fresh air into my tent. The problem with sucking in a tent is if the pressure is not right the walls of the tent will be sucked in and possibly knock over the plants or fans inside. I have the 4 inch fan turning on for 30 minutes then turning off for 30 minutes, mostly to cut a bit of energy cost. It's been working for me so far the only problem before was the air being pushed out was not being scrubbed, hence the new intake filter and re-positioning of the carbon filter. By having a completely separate fan for the hood I am better able to control my temperatures in the cold weather by simply raising or lowering my fan speed controller. All the while not messing with the fresh air coming in and out