I put holes in my boxes when I put them together, but only if I remembered :)
My bottoms are all the way open. I only used a reducer a few times and that was when I thought there was robbing happening. Oh yeh, sometimes I used the rducer at times when I thought it would make bees that I caught stay in the box. I found out that if they wanna leave they're gonna leave anyways. I found that when I catch a swarm the left over bees like to go through the hole more than the entrance. For me, I can look at the bees better when they use the hole because it takes them longer to get in. I put the holes in for ventilation. I've read recently that some people are saying that they regret ever having put the holes in the boxes. I have holes in the fronts, the backs, the bottom boxes the top boxes, and no boxes....When I get to putting boxes on or moving them for whatever reason, I forget about the holes(not intentionally tho :-\) and the holes just end up where they end up. If I remembered, I'd put them in the front top box!
I would use screened bottom boards too, but I made a mess of regular bottom boards...I'm thinking of cutting holes in the bottoms with a hole saw.(just for airflow, not mite control)
Its hot as heck here too! sometimes 120!...I like the holes too...Since I started writing this, I've been thinking about putting a design around a hole just for effect...Like the center of a daisy or something like that...Maybe a belly button of a person! :-D
Oh boy,......Theres all kinds of ideas churning thru my mind right now!