When I changed to OMFs, I also was changing to 14 x 12s - more space for the bees, should the weather be really bad, to move up (without having the pain of over-wintering on a brood and a super). Doesn't seem to be an issue with a deep drood only, but I was relatively inexperienced and didn't want to take the chance at the time.
My first winter last year and I aquired some nuc's late season that were big enough for 14x12 frames as in they fit in, but you could see the bottoms of them through the entrance hole. They went through the winter like that, plenty of food and every day it was cold (down to -18) I worried about them.
All came through and built up nicely in the spring and gave a crop this year.
Pete D