hey dd,
i think your own assessment is probably correct with what you described.
what perry asked~
"Was the screened bottom board closed, as in the tray was left in, or was the bottom entrance closed off alltogether? Also, what size holes did you use for upper vents?"
you and i have similar weather in wisconsin. this is how i winter my bees. i don't use SBB's. just a bottom board. entrance reducers at 3" or more, or left off. i wrap my hives in a material from b and b honey farm, out of houston, minnesota; 'colony quilt'. my inner covers have notches cut out in them 3 to 3 1/2", notch down. i place 2" of polystyrene (the pink stuff) under the outer cover on top the inner cover, you really don't need 3" of this here in wisconsin. i also put a shim on if i think i might need one; a 2" incher, but it goes under the inner cover rather than over the inner cover. i like to put feed on the bees if i have to in an emergency so that it is right over top of them without the barrier of the inner cover. but have done so over the inner cover. i have also left the shims off because the winter patties i use fit underneath the deep side of the inner cover. with that said, i keep russian bees, they are conservative on honey stores, so don't find the need to feed them fondant or winter patty until very late winter when temps are conducive to slide feed on top of the frames directly above them. hope i made sense?