Using the plates for the dual line systems was never a problem for leaks (see note). There was never an issue with suction with the spacer plate unless something wasn't tight. The only real issues were blowing the gasket at the filter adapter because it's on the pressure side and drainback, which seems to have only been a problem with the milodon pump.

Note...I had to grind one edge on the block face of my spacer plate for it to fit flat to the machined surface. I suspect it was more an issue with the factory block machining than with milodon. trial fitting things pays off!