I haven’t had to deal with SHB here, but I’m a bit confused how that 3/16 slot is supposed to work. Are the beetles suppose to walk in, crawl down the U shaped depression into the hive and then fall in the crack as they try to crawl up the other side? I just figured the beetles would fly right over that U channel when entering the hive, but I don’t know. Beetles are pretty small, why walk when you can fly?
I agree with Jim, all that landing space on the top of your bottom assembly is not the best idea for varroa. They’ll land on that wood and then catch a ride with the next bee back up into the brood nest.
Looks like a good first revision to test with and modify as you observe the bees and pests reaction. Sounds to me Royall that what you REALLY need is some bees of your own! :-D