@thoughtsofawho This design could be push or pull across filter, and while the sack doesn't exist as a product, I'd make the argument that perhaps it should or could simply, as it is formed from a rectangle and has 2 seams. The circumference around fans above is 8 x 140mm = ~44 in, and a factory roll is 32" (I think, don't have my supplies, could vary idk)). So, a rectangle 22.5" x 32" that is is folded and glued along seams to produce a 16" sack . Is this enough surface area for optimal fan performance? Perhaps. (A goal would be to effectively utilize factory roll/ simplify manufacturing process. This same method can be used for varied arrays or matrices, if can deduce optimal surface area per fan.) I'd point to vacuum bags as comparison.