As pointed out, the manual states that something around 3100 rpm is going to give you the "recommended" 540 rear, 2500 mid pto rpm. In my experience using a box mower, sickle bar, post hole digger, and just recently mmm, I have to agree with those who suggest using whatever seems to work best.
It took me a long time to realize that my 5' brush hog worked much better when running at the full 540 or even a little more. Much less bogging down or clutch slippage because it had the momentum to just power through just about everything. Of course, on those occasions that you hit a rock, it's even more unpleasant. With a sickle bar, on the other hand, I find it works well at very low rpm, much less than 540 to the pto. I definitely do not want to run my phd at 540, way too fast. MMM seems to run great at a little less than 540 pto.
Unless someone can tell me how running things at less than 540 pto is going to harm the tractor or the implement, I'm going to keep doing it.
It took me a long time to realize that my 5' brush hog worked much better when running at the full 540 or even a little more. Much less bogging down or clutch slippage because it had the momentum to just power through just about everything. Of course, on those occasions that you hit a rock, it's even more unpleasant. With a sickle bar, on the other hand, I find it works well at very low rpm, much less than 540 to the pto. I definitely do not want to run my phd at 540, way too fast. MMM seems to run great at a little less than 540 pto.
Unless someone can tell me how running things at less than 540 pto is going to harm the tractor or the implement, I'm going to keep doing it.