Re: screened bottom boards
> Are there any similar guidelines for allowing pests like SHB to fall through?
Your only options for suitable hardware cloth to allow SHB to pass are #7 or #8 as other sizes (smaller numbers) allow bees through as well. #7 hardware cloth is quite difficult to find, so for most beeks #8 is the only practical choice.
Betterbee does show #7 hardware cloth on their website, but it has been "out of stock" for a long time. I don't know of any other source for reasonable quantities.
ultracrepidarian >> noting or pertaining to a person who criticizes, judges, or gives advice outside of his expertise