I've got them on about 5 hives now. I cut a groove so I can insert a tray/closure board, but haven't made any yet. I may eventually make a tray or two to insert so I can check what drops out of the hive (perhaps mites). I don't ever intend to actually close them for winter, or any other season.
I am thinking of trying MB's idea of upper entrances. My plan is to make a couple of those queen rearing bottomless bottom boards that you can put on top of or between supers and then while leaving the SBB in place, close it off as an entrance, thereby making a flow-through ventilation situation with the entrance on top of the 3rd medium brood super and medium honey supers above the entrance. But I might put it between the 2nd and 3rd to reduce the chance of large amounts of pollen being stored in the honey supers.
Another idea I plan to try, is to create a clustering box of slats about 4 inches deep with an entrance cut into the middle of one side. Sort of a cluster area/entrance that can be positioned below, above, or between any supers.