quite a bit. I spoke with Victor one of the engineers from ATB yesterday. His advice was to not exceed 2000 l/h of air input. also with this particular cone size, to not exceed 32 inches in total height. I never realized how inexpensive this project could be compared to buying an actual ATB. Im certainly going forward with it. At the very least i could let everyone knows how it goes, i have 2 sedra 5000 and 1 sedra 9000 sitting around to test with if need be. but id much rather get a decent pump instead of a sedra. this is certainly not a crap shoot.
If a mold is route everyone would like to go. ATB uses a mold that consists of 2 wooden rings(one on top and bottom of cone), where they then put wooden vertical struts and then they fiberglass it.