Hi @johng -
Those impellers were just a random size, based on what was easy to 3D print! I believe they were ~2mm in thickness, and an arbitrary paddle-wheel geometry. Certainly - experimenting with different numbers of paddles, and their shape / tight clearance with the housing will definitely drive the resulting performance of the pump.
Moving 60GPM via venturi may be beyond what the M200 can manage… 6GPM seems a more realistic target for this, at best, based on my recollection of how the testing went (not very well for the pictured design - maybe 1-2 gpm? but M100 was not drawing its full potential power, and you have more available with the M200.)