Ok - i’ve screwed up three glass engravings trying to do it without the crumb tray, and using math. Each time the engrave has been substantially high and to the left, and about ⅔ the size it shows on the screen.
Another user has created a “no-math focus ruler” that I plan to try next. (No-Math Focus Ruler)
So here’s my stupid (probably) developer question: - Wouldn’t it be relatively simple for the developers to put in a toggle in the interface for with/without crumb tray, and then just measure the depth of the item you want to engrave? If it’s over/under the allowable focus, that should be an easy warning trigger.