Hi John, not done this myself yet either but i assume measurement is taken
from carb body to bottom of float (flat side) central to the float if you know
what i mean. for the older carbs there seems to be an issue whether to measure from top of lip or gasket surface,but as the F2 carbs don't have this lip, it must be from gasket surface?
i know these aren't your carbs but this might help clarify the matter-
as i said before, not done this yet so if anyone knows better please explain, as this is how i intended to do mine,
regards,
Ed.