6 out of 7 living. I think that not taking too much honey in the fall really helps, but I really think that it was because I gave them a sugar treatment after the queens were done laying, that when all the mites are out on the bees...
Anyway the one that died, I think from the condensation running right in the middle of the inner cover. all the other hives have little shims to tilt them forward, that one was dead level.
BTW, it would be interesting to find out how many over winter theirs on screen bottoms (all of mine) just added one inch of foam insulation to the top of the hive, above the inner cover and of course a BIG rock on top...I also think the rock is key!