What Flexcube permeability shall I use to ferment & mature Chardonnay?

Because there is plenty of O2 available during ferment, the permeability of the Flexcube is of little influence during fermentation and immediately afterwards (say 1-2 months). So you can ferment in any permeability. For maturation, however, LP is highly recommended (essential). Chardonnay and other white ‘broaden’ and ‘fatten’ quite quickly in MP Flexcubes