I think you are on the right track here;at first I thought I was going to need to come up with an active intake, but I started with a passive set up - 4" - at the bottom of my tent and now I have all the negative pressure I can stand. I have a 600W in a 4X4X8 tent / 170cfm fan/filter and I get plenty of airflow. Also get a small, clip-type desk fan to circulate air inside your space. It can be a little trial and error, but once you get that first nice harvest you can be proud!!