Re: Cluster at the very top
Studies done on hives wintered in the north showed that the cluster moved or started in the bottom box in fall and moved upward during winter. I will assume that the researchers observed this in the majority of hives.
Walt has a good point on honey stores and no doubt some clusters will behave differently depending on feed location.
Most northern hives are packed away in Oct/Nov and because of weather are not inspected until Feb/Mar so it makes it hard to know exactly how and when the cluster moves. When I ran doubles a few clusters were still in the bottom box in March, some were half way up into the top and some were mostly in the top box.
Now that I winter in singles the cluster is hopefully found where I left it.