The hives were lighter than I thought they would be. This drought is tough.
So, I'll check on them during a warm spell, which we nearly always get in winter. Won't have to disturb them too much to do that. Put transparent bird feed sack material on top of the fondant and then the lid, which straps down. The lid has 1-1.5 inches headroom -- plenty of room for fondant.
There's room for more insulation under the lid, too. So, I might add some Reflectix.