First off, I am a Newbie grower so I am nowhere near an expert, but I just went through this same problem (my tent is about a 1/3 of your size) so I think I can offer some help. First off let me ask if you have your intake drawing in nice cool air from the outside? Also if your having a temperature problem in a larger room you should have a fan capable of evacuating the room at least 3-5 times a minute for optimal cooling. That means your fan should pull anywhere from 2160-3600 cfm a minute. Most budgets don't allow that, so you should have a fan at least capable of 720 cfm which is 1 time a minute. If your using the booster fan as an active intake that should help your more. Also is you exhaust/intake system ran in a closed loop? Meaning your intake is drawn throuh the vent the goes straight through the cooling tubes on your lights and out the exhaust? That should help cool it down as well and will keep up the humidity. Hooking it up that way along with running your ac at times (if the temp spikes up a bit during the day) should get your temp. to where you want to be and still keep it humid enough. Hope this helps feel free to ask anymore question if I didn't cover enough