What we sometimes did in such a case is we placed an empty opening the size of which was the same size as the two windows combined.
Then we added an Element ID to the empty Window, made the Element ID of the two Windows blank and scheduled the Empty Window.
This way sizes were good.
Not good if you want to have 3D side Views in your Schedule though.
We also turned on the Marker for the Empty Window, turned it off for the other two Window involved.
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