On my opinion it should be perfect, should be 1=1, if it`s not perpendicular then I think you need to re align the machine itself, put washers or loosen bolts and hammer it with rubber mallet then tighten again, any method to make it perfect sir. usually CNC machines gets offsets or misaligned during shipping and handling (rough sea vibrations on the units itself) one of our machines got warped when they delivered it to the shop. a simple loosen tighten resolves the misalignment