Actually. wintering two vertically is rather unusual among commercial guys. Its a PITA lifting everything off to get at the bottom one, so as soon as both halves are demonstrable viable in spring they get split off into individual hives at the time of shifting to OSR.

This far north it has proven futile (more in the economic than the absolute sense) to overwinter small mating nucs. The poly ones on full frames less so, in fact they are doing very well this winter again, have several hundred ready for spring market.