The string and 2x4 got mine set pretty well. Also, going 2mm out on one side, then 2 out on the other to round out the difference makes it easy. Having digital calipers available to track the movement is good too.

As mentioned, I did "overshoot" as I was incrementally adding force, and spaced myself out to 140 on just moving one side. It didn't look like I damaged anything though...