I've got several eight-frame medium nucs that will probably be overwintering in one or two boxes. I was tentatively planning to stack them for the winter with 1/4 plywood between hives.
Then I was thinking about simply using migratory covers instead of plywood, i.e., the cover for one hive would be the base of the next. That way each hive gets a top entrance.
And while I'm at it, is there any reason conventional bases wouldn't work? They'd give each hive an entrance at the bottom and ventilation at the top.
So picture maybe three hives in four, five or six boxes total, stacked from strongest to weakest, and topped with an insulated cover.