The Good Doctor is right about the 1000w bulb in a 4x4 tent. I just bought the exact same tent and they recommend the max at 600w, I would change it to a 600w asap because a 1000w in that tent is kinda a fire hazard. Using a 6 inch fan should work great for you, that's what size I will be using for the online & exhaust. Might want to place a small fan on floor of tent blowing up to help cool the light off. Other then that I wish you luck with you grow, can't wait to crack my kushberry seeds open.
edit: Sorry about that, I posted this last night via iPhone & did not realize the thread was 16 pages long already.