If you will take another look at the link you will see that the source for all the air is behind the fan.
I have an idea Mr Bogart, how about you buy yourself a couple of inline fans (I can personally recommend Vortex and Fantech as I own both and have had good performance with both), hook one up the way you are sure is best and one the other way. Then you can decide and offer advice based on experience, as I am doing. I have set up my own grow system, well documented here, and well as systems for friends so I have experience with these fans in actual use with grow boxes. I am sure your HVAC experience is valuable and you are no doubt competent at what you do, but I can tell you I have set this stuff up myself, both ways, and have talked with and read the materials the manufacturers provide and the information I am giving is sound, correct, and applicable. As for my qualifications, heck I own my own lab and personal care products manufacturing compnay. I do actually have a clue friend.
