I did my hives the same as Rae.
The message is getting through, but only slowly.
I am never too sure about a fully open OMF under just a standard brood box - I would prefer a brood with super above - but it has worked for me for years. I am certainly confident with a brood and a super or, in my case, all 14 x 12 broods.
No condensation and no losses down to the OMF - in that any losses were among other hives over-wintered under the same regime and on the same site.
It works. Yes, stores consumption will rise, I will accept that, but it would rise much further with top ventilation as well! Possibly to the extent of approaching the risk of 'isolation starvation' where the cluster cannot move to fresh stores due to very cold temperatures at the time of a required move. It has happened to me.
The idea is not to worry too much about the cold as long as there are plenty of accessible stores and no damp in the hive. Satisfy those two criteria and a colony has the best chance of survival, provided it goes into the winter strong in numbers, healthy, is Q+ (and she is laying worker brood!), has relatively light varroa loading, is neither subjected to extremely high temperatures nor ferocious draughts directly into the hive.
Even when Q- (or with a drone layer) a colony can survive the winter as long as remedial action is taken early in the spring. Not a good position if only one colony, I agree, but there is always a glimmer of hope if there are bees in reasonable numbers.
Not too much trouble for each item individually, but all parts should be considered in the best plans. Having said that, there are colonies which survive the winter without even all-round protection. But why take any unecessary risks, especially if one lost colony represents a 50% or 100% winter loss?
Those of us with multiple colonies expect the odd loss and sometimes higher losses occur in, say, one particular apiary or area for unknown reasons at the time. These are unavoidable if, for instance, a new virus is intoduced in some way (I always blame imported queens in these instances - one reason I don't import queens myself!) and are expected from time to time. We just get over it, breed more queens from the remaining resistant stocks to make up the losses, and simply carry on. The bees are the important thing for a beekeeper.
No bees, no longer a beekeeper (until restocked). BTDT, too!
Regards, RAB