Two days ago I put the entrance reducers back.....
I've went down a few times to see if any bees where using the new entrances yet.
Uhh, Bees are slow to change entrances. Two days is nothing in the colonies memory. Don't expect instant response, honey bees have evolved to be conservative in their responses.
I think 1/2" holes are undersize for entrances, and the bees will close them up. I drill 1 1/8" holes (in traps and nucs) (and cork these with champagne corks). Normal wine bottle corks are 7/8" and that size will work in a pinch.
My experience is that the bees like to have the core (brood) population close to the traffic flow, and vice versa. I use this propensity to fill the lower deep with brood, I entrance reduce with a 10-12" block of 2x2 on one side of the bottom board-- the brood moves to just above the side entrance (filling the frame 1&2 with brood). I then slide the block to the other side, and the frames 9 & 10 get brood. Normally 1,2 & 9,10 have pollen and honey stores, but by pushing the brood out to outside, you can have a summer deep with all 10 frames going off.
The advocates of top entrances claim the bees are more efficient because foragers don't have as far to walk. I have seen no evidence-- it sounds to me like projected (aristotelian) inductive logic. My observed behavior is the bees are social, and want the contact with the nest, and don't care to be shuttled off to the supers to ditch their load like some beast-of-burden.
My problem with top entrances were the bees completely abandoned the lower entrances in time -- and the brood nest move up close to the top entrance. This contributes to robbing, and real management problems when efficient harvest assumes taking honey supers off the top.