How to measure collective and cyclic pitch max and min?

[ZeXx86]

We recommend difference under 0.2°. But it is always dependent on the pilot. Some can't distinguish any difference even with 2°. But for precise flying it is recommended to have no measurable difference.

[ujovko]

Is it important to measure it so accurately?
We should perform "main rotor tracking adjustment" during flight. (Yes, I know, it's almost impossible without a right and left threaded rod.)

[ZeXx86]

It is not important but advised.

Main rotor tracking can be made very easily as described in the guide posted above. No need for left/right threaded rods.