I started using a fixture like “ConvenientWoodwork” posted with my friends dial indicator but because my spoil board is a couple layers thick there wasn’t room to rotate the arm past the X Axis beam. Then I realized I didn’t need a dial indicator. I can just use the Z probe to measure each side and compare the absolute value of the probe on each side.
I used a quarter inch rod in the router end and a quarter inch screw at the probe end. I rounded the end of the screw to help ensure a consistent point of contact. This worked out very well and avoids the need to purchase a dial indicator.
Another advantage of this method is that the Z probe averages out the height of any sawtooth pattern in the board which would be a problem if you probed one side on the high portion of the sawtooth and the other side on the low portion of the sawtooth.
