the measurements to the outer cuts is finding the effects of chain sag
but we need to do two central cuts so that we can solve the different triangles
to figure out the proper rotation radius. If we leave this out, and try to just
figure out the rotation radius from the effects on the outer cuts (where the
chain sag effect is maximized), we are not going to accurately figure out the
rotation radius.
In the earliest version, we did a cut in the top center area. This was moved
down to the lower center area because Bar was getting bad results due to his
frame flexing.
We cut wide to maximize the effect of chain sag.
we should cut high center and low center to maximize the effect of the rotation
radius
This is one additional measurement, but without it, you seriously reduce the
resulting accuracy.