I have seen all sorts of complicated ways to make measurements for objects thicker than 1/2 inch and removing the crumb tray. They usually involving multiple measurements, calipers, multiple equations, etc. Here is an easy to use template where you can set you parameters and get the results you need. If someone sees a flaw in its design, please let me know - but this has worked well for me.
When the set focus tool actually set the focus, most calculations became unnecessary. I use the no math focus height tool to make sure I am within the 1/2" focus range and then use the set focus. Very simple.