You need mower input to turn at 540 rpm. Don't know what that is? Buy, borrow, rent a photo tach. Where pto output is at 540 rpm, put a mark on your throttle plate. My tractor that is near wot (2650 rpm out of 2700 rpm). How fast to mow? Depends on conditions. The fastest I can reasonably mow is 4.5 mph, cruise control at full forward position. Just happens to be mid-range gear (2 out of 3), low hst (1 out of 2) on my tractor. Anything faster than that and it is too bumpy for my property. Don't know how fast you are going? Use your gps (tom-tom, garmin, etc). Experiment and have fun! As long as the cut quality is within your limits, you are doing it right. Philip.