One common method of setting the MagnaValve shot flow rate is to increase it until you reach the motor amperage limit (subject to wheel RPM etc). However, running the maximum flow rate doesn't necessarily relate to preferred operation. For one thing you could be flooding your target surface and not get the intended effect. For another you will be breaking shot at its maximum rate thus increasing your media consumption consts. I would recommend that you start at some low shot flow rate (I presume you use an ammeter for indication)and test to see if you get acceptable results. Increase the shot flow rate to see if you achieve results, coverage, any faster. If yes then continue in that direction. The object is to run the machine at the lowest flow rate acceptable to proper results. This mimizes shot breakage and machine wear. If you are using a MagnaValve with built-in flow rate sensing then the same plan would work, just start a low flow rate, perhaps 100 lbs/minute and observe the test results. You may discover that the two wheels will have different preferred flow rates since one is down shooting and the other is a hip wheel.