I noticed that CURA does not say anything about the valid range of values for the initial layer… LulzBot CURA manual gives a warning
Your LulzBot Mini auto leveling system could be affected if you change this from the standard profiles. Adjust at your own risk.
but gives no further information.
For example the functional part I designed in SolidWorks has a consistent minimum height of 2.25mm, and sides are all vertical. 2.25mm doesn’t really sound realistic, but CURA accepts the value without any sort of warning, and the calculated print time becomes ludicrously low. So how thick can the initial layer be?