4x4 tent suction

I just bought my second tent, its a 4x4, I have my 6''in exhaust fan running at a lower speed, but still causes a lot of suction on the tent.

This is the tent
http://www.ebay.com/itm/141134537401?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

My problems is, I can fix the suction by opening the vent flaps but that will cause light to come in/out

How do you guys with large tents deal with lightproofting and suction?

Lol...such an easy fix...that's "negative pressure" a good thing, a required affect! But it takes up width inside and minimizes room for plant growth. So get a board,pole long enough to brace the sidewalls in place...the suction isn't that strong..I have poles positioned diagonally for this purpose...or...cut white(reflective)PVC pipe to fit between the framing poles of the tent horizontally to keep walls in place..PVC is very cheap! If my lights were on I'd take a pic...but not til 3 Cali time...

I use bamboo on the inside of the tent.

you can also get a 6 inch inline duct fan keep it outside on the floor for coolest air. the blowing in will reduce the suction. exaust hot air out and intake blowing fresh air in.

I have 2 4x4x7 tents. both have a 4" intake booster fan and a 6" booster fan for exhaust. I have the perfect negative pressure.

Keep the intake open and put something in place to keep the light out. I used to have a BudLt box there with some screen on one end, now i have a L shaped duct piece.