Hi there. I've got a Preciso, too. The other day I was messing around with a kitchen strainer, using it to sieve my press grind (setting #34F, if it matters). I don't know how big the spaces are in the metal mesh, but a 1000 micron (1.0 mm) steel ball bearing doesn't quite fit through them, so it's probably close to what you asked for. Anyway, I gave 21.9 g. of my press-ground coffee a thorough shaking using this strainer and ended up with 20 g. of ground coffee remaining. That's only 8.7% loss. Not bad, right?
What was sieved out:
A closer look:
Bottom of the cup brewed afterward in my Eva Solo 0.6 L (damn, I missed a few fines!):
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