Sounds like you're trying to use an extremely inefficient horizontal unit in an efficient vertical mode. That just doesn't work.
Ya gots to build an efficient vertical unit based on physics. (Currently there are ZERO commercial options for such) I'd tell you how I do it, but then again I might want to commercialize my system... Yeah, I know, this makes me sound like an ignorant self-aggrandizer....
But remember, heat travels UP naturally and plants require more air agitation than exhaust (ie, there is NO value in containing the air flow within the garden to a tube), and light travels in straight lines with zero loss per foot of travel. From there, you can build something easily 30% better than the best offered commercially.