rdy-b and annette,
That's where I got my original design and it has worked fine so far.
From original pictures I can see that the big hole is for feeding, not ventilation.
In winter position the hive has awfully much holes.
In summer the cover is turned so that there are no ventilation much, only upper entrance.
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My experience is that it is terrible system .
I have same covers all the year around and I can vent the hive so much that they need. The need is very small.
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In Finland , of course we have a big debate, whose inner covers are best and whose are nothing.
But still all hives do well with theirs system.
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