Mentioning a number of millimeters IMHO doesn’t help, because it highly depends on wheelbase as well. Shorter wheelbases can have much less clearance and still be just as functional. A long wheelbase needs a taller clearance, or a clearance that’s arched in the center.
My goto test is I go find a speed hump local to me, one of the nasty ones, and I like the skate to just barely be able to roll over it head-on with me on top, without scraping (but a couple millimeters away). The shorter the board, the lower it can be.
