using the level mill table as reference, and with the RRS plate on the cambo, all resting on the table found i needed a 0.020" shim under the front edge of the RRS plate to level the sensor F/B
RRS plate is 2.16" long, so a .020" shim is about the same as 1/2 degree. plate thickness varies end to end about .003", which contributes.
did the same with the RRS plate removed, needed a 0.006" shim (base is 1.06")
i am going to machine the RRS plate to get rid of the .003", then fit shims between the cambo base and RRS plate