I asked bitmain about the static pressure and no answer.
I guess I will have to pay a lab to get the info hehe.
You have your answers - if you are ducting miners you MUST use a fan/blower at the outlet of the ducts that can move at least the same CFM as the combined miners do. You CANNOT use just the miners themselves to do it. If you just want to ignore what has been said here, sure, go ahead.