[sparkycuda]

You are describing an open-center system - pump discharge goes through the valve & back to tank in the "off" or neutral valve position. As you open a valve to direct oil to a cylinder, the return-to-tank port is proportionally closed. At full -open to cylinder, the return port should be fully closed. This allows max cylinder speed and the pump can provide max pressure, which is now regulated by the system pressure relief valve. If the tank port is open at valve full-open, you will reduce flow to the cylinder and the pump will have to overcome flow loss and pressure reduction. Remember that flow goes to the path of least resistance, so any passage to tank will happen first and system pressure will be limited to whatever can be produced with the tank port open. This can work, if the pump has some extra flow capacity.

Ken