I have an old Navy buddy down in Kentucky that is also a struggling beekeeper. He was up here about three years ago and found me working at the problem and now we trade tidbits when we can.
I told him about the bottom screens to reduce mites. They have been using that method for years but don't put anything below the screen. I'm sure their weather is warmer and the season longer so they just leave the hive bottom open.
Something else they do is put a paper towel saturated with vegetable oil on top of the upper super. The theory is that the bees try to rid the hive of the trash and in the process coat themselves in oil that repels the mites. He says it seems to help.
Has anyone heard of such a thing?
Another thing he is trying is starting with a larger package when he starts a new colony.