We run our L5740 and M8540 at 540 plus or minus a bit, may bog down a bit in tough stuff going up hill. We use a LP RCR2672 on the 5740 and Woods DS1260 on the M8540. On the M8540 if it bogs down a bit I will use the foot throttle temporarily to kick it back up a bit, but only if it drops quite a bit.
The Kubota seems to really be running high RPM in comparison to the old Ford, Case, Massey Fergusons we have, but you get use to it.