Never store empty supers above a slotted inner cover.  That's what I did
and the result was the starvation of a nice colony of bees.  There was
plenty of honey in two deep hive bodies below, but during the late winter
they moved up into the two shallow supers that I had put on to be cleaned up.
The probable reason for the movement of the cluster upward through the slot
(size = approx. 4 cm X 12 cm) into the empties was probably the fact that
is was warmer there on a sunny winter day. The lesson is that cluster and
honey stores must not be separated in cold weather.
 Bill Morrison
Southcentral Pennsylvania