Re: Migratory Lid Plans
If you actually build a spacer (bigger than bee space) that you can't remove into your covers the bees will surely fill it with comb in the spring.
I Make mine out of Advantech and instead of cleats I use square blocks attached so that just the corners touch the hive body - thus giving hive beetles one less place to hide. The advantech is very durable and warp resistant, but if not protected from the weather it will dish slightly upward over time and hold water. I cover them with trim metal which seems to keep them fresh forever.
Don't let what might be best prevent you from doing what will work.