It's been awhile since I've used any CMM software, but will this setting keep the datum structure, but still allow it to rotate about the origin for best fit? Datum A is 3 points called out on a canted curved surface (and not a cylinder), Datum B is a nice straight line on a flat wall, and Datum C is a point on a flat wall. So I believe that my results are being skewed from Datum A if it's not picking up the points exactly. I normally don't use Bestfit, but I'm getting conflicting results compared to physical hard checks (micrometers and such) when not using it and closer results when using it. I am fairly certain that it is an alignment issue.