Bed Level Correction process

(2021) Thingiverse seems to have destroyed / lost multiple additional stages of instructions and reference photos. I'm not sure it is worth recreating given the advances in automatic mesh bed leveling.

Work-in-progress... would be delighted to incorporate suggestions for improvement. Please comment or message me.
* 2019-09-11 @wabbitguy suggested connecting the patches to make it easier to keep straight which is which while measuring. Was such a great idea, I had the .scad file updated almost before he sent me a picture. Also added an option to overlay an "X" and "Y" on the connections near the bottom-left origin patch. However, when I first tried to print it, the adhesion on those long skinny lines just didn't hold and made a mess. So I've included a new FirstLayerConnected.ini print settings file which turns perimeters back on but prints them after the infill.
* 2019-07-20 Modified version will *not* recommend changes to live-adjust-Z but warns if patches are >125% of nominal