Have no holes drilled in any of our boxes. Just too inconvenient at migration time.
However, at certain times and in certain circumstances we DO stagger boxes.
1. As part of demaree, to allow the drones hatching from brood that is now above the QEx to fly free and not end up dead on top of the QEx causing serious issues for bee passage.
2. In very hot weather and very strong colonies as an assist to ventilation. Its amazing just how quickly it reduces 'hanging out'.
3. Very strong hives in heavy honey flows. A ventilation assist again which speeds up the ripening process (at the Ling especially, which can have very thin nectar in huge volumes if there is a heatwave after a good soak.)
4. Tall colonies containing a mix of box sizes, as Hoffmans in the deeps and Manleys in the shallows gives rise to an impeded air flow which can hamper yield. The stagger partially helps with this.
5. After reuniting requeening spits back to the mother colony. Helps the bees to find their home without having to run down the surface of the hive and get access through the broodbox that is not their own.
We are using Smith and Langstroth hives and the stagger only opens about a half inch at the front, over the lugs, and because of the box wall thickness you can carefully set it so there is no rear entry as well. Rainfall is then not actually important as any that goes in will just run down the internal box wall. Its not directly falling rain thats the issue anyway as the amount that hits the stagger is minimal, its driving rain from the wrong direction, hitting the box face above the stagger then running down it. A rare occurence not really worth worrying about. The stagger is eliminated as soon as it is no longer needed, as it can lead to excess ventilation by convection heat rising out of the stagger. It is never needed on hives that are less than four, even five, boxes high.
Look up the 'Imirie Shim' for a US origin gadget that tackles this issue. However, if you are really NOT fussy just stick a couple of little sticks or wedges in between the boxes one the sidewalls almost right at the front. Small amounts of ladder comb can be an issue in these cases.