Tree build stopping criteria: is the number of mantissa digits the right thing to stop on?

I think that the changes in !41 (merged) may be overly strict in the number of levels to stop on. They do not take into account differences in the length scales of the points. In practice it is possible that geometries resulting from dyadic refinement may contain points at more than more than 52 orders of magnitude. See here for an example where the smallest length scale is 10^-30