Another possible advantage of over-wintering in a ‘vertical arrangement’, particularly a well insulated one, is that the cluster will almost certainly move upwards as winter proceeds, consuming all stores as they proceed.
That means as long as they do not run out of stores they are unlikely to get caught out by a long spell of very cold weather after brooding has started - and then succumbing to isolation starvation. BTDT. As stated above, stability could be a problem, but a ratchet strap (or two) securing a block of wintering colonies works wonders on that score.
I had a colony which easily managed to survive for a couple or three seasons in a 5 or 6 frame 14 x 12 ‘nucleus’ with one or two same format shallows above. The boxes were basically Dartington honey boxes and 1/2 sized Dartington supers made with 6mm ply sides. Those bees had little or no attention in that time as I was recovering slowly after a quad bypass operation. Some scum eventually stole that colony and although the police (eventually) got the scumbag, the colony was destroyed by his interference.
IIRC they were only provided with a proper open mesh floor part way through that first winter. I only had two days notice before hospitalisation late in September, and they really needed some attention when there was more than a couple inches of snow in the middle of December or early January. Two hives got attention that day - that one and another that was a rushed queen change/unite with only a Dartington 1/2 super above a full sized National box with a horizontal board covering the other half of the brood box. The snow at least needed clearing off and a better covering arranged. A long time ago, now.
