Got 2 650 CFM Dust Collectors. One is the Jet the other is the pretty much the same model but it is a Sears Craftsman. Never used the Sears Dust Collector . It's just been sitting in the corner of the shop. Now, I have that old Sears Craftsman Whole Shop Dust Collection System , that Sears sold 20 years or so ago. It's got the 2 1/2 " clear pipe with blast gates, etc. If I run all 2 1/2 Inch pipe around the shop, and then connect that 1/2 pipe system to 4 inch flexible dust collector hose; what might the reduction in CFM be ? This is assuming that I would be running 1 machine at a time. Would I need to run Both Dust Collectors , or would 1 be good enough ? Shop is 25 x 30