I think Hoot bailed on the deck levelling thing.
I have found that getting the deck level, & matching the cut height knob (With actual cut height) can be somewhat taxing on my patience. I have previously commented on the fact that in order to have the cut height match the scale on the adjuster knob, the rear adjuster bolts have to be nearly bottomed out. A condition that was made slightly better with the addition of HDAP rear tires. I have also noticed that with the blades perfectly level, the anti-scalp/gauge wheels are not even. Their clearance is different from side to side. (Though not critical.) It would be nice if they could be adjusted independently of the deck/blade height. (Other than the 1/2" spaced holes.)
I have checked my deck several times since I bought my X540. It has held adjustment pretty well, and does cut nice and level. But, I certainly had to adjust it from when it was delivered to me. The factory deck height was not even close to the height on the knob, and it was way off level. The selling dealer should deliver the tractor with the deck levelled, don't you think? Do they assume that every owner is going to take the time that many of us do to get them cutting nice and level? I guess they must, because I did. And so has every else that comments on this forum.