Aha! Next step is to make sure the boot fits the same way and that the tray stays level within tolerances. I did this by measuring 4 points along the edge of the tray with the plunger of my calipers both before and after booting.
lower the plunger:
place into position, square against the edge:
The tolerances stayed about the same for me.
Don’t bother doing this while you’re still an invalid!