Xerox, You want to avoid chilling the bees. With that in mind;
are there any stores in the bottom box? Common during winter for bees to move upward in a two deep hive. In my area, Arkansas, it?s still to cold to tamper with or adjust the boxes. I don?t know your high and low temps? If it is cold, 45F and lower, I would leave the lower box alone even if empty.
Blessings