verify keyway position

I believe the "correct" way to measure this is to measure points on both planes - the pattern of points must be the exact same - and then create midpoints between each point corresponding to the same point on the other plane (ie. mirrored pattern). From these midpoints, construct a plane that you use for evaluation/s.

I used a similar way. I generated two planes on both keyway's sides using symmetrical points.I generated the first one and then the second, just  switching the sign of the symmetry plane. From these two planes I made the midplane and I eveluate its coordinate.

Can this strategy be strong like yours?

If you already have the symmetrical points method as measurement, create midpoints between them and create a plane out of the midpoints that you use for evaluation. See the difference.

If you already have the symmetrical points method as measurement, create midpoints between them and create a plane out of the midpoints that you use for evaluation. See the difference.