Yeah, you wouldn't want to just inflate the tent or room with positive hepa pressure, and figure its good to work in like that. You would still want to work right in the laminar flow coming out of the FFU or hood, within a a foot or so from the filter. Yep, most FFUs are made to put out around 100cfm.. a little more without the prefilters on. I still think even with positive pressure its a good thing to scrub the whole room though even with one extra hepa unit/FFU, as long as it doesn't interfere with the flow from the main work hood , which it shouldn't. Clean rooms use a crap load of FFUs to blow down from the ceiling, and actually do achieve true laminar flow through the whole room with that many going at once. They still put flow hoods in the same clean room though.
Having a single large FFU either ducted in or ported right through the wall in the tent won't produce laminar flow all the way through, but the positive pressure will keep the tent from sucking in more contams through all the zippers and cracks. Even though it will be slightly turbulent, it will still flow good enough to vent the whole tent with filtered air going one way, which would likely be out and behind through one of the vents.
