It is also evidence of roughly how much tolerance you have. The error doesn't vary much across this range. The support points move quite dramatically, to .19 and .64, with relative force of 3.3. In fact, that's roughly what happens. Click here to see the output.
Sensitivity becomes a concern at large diameters.
At this point, design becomes a little more intricate for the thin glass that we assume. However, studying the error as diameter is varied leads to a new surprise. Error grows much faster than the square of diameter, as was previously the case. The problem is that at this scale, the sagitta becomes significant compared to the thickness. We need to adjust the support radii as the mirror increases in diameter.