Here in the tropics 14x12s tend to do ok, in the lowlands of Bristol (and with the bees around there) they can even be a bit on the small side. I contemplated a bailey change but figured boosting the nationals should help ensure half the colonies bring in some honey. I’ve been on 14x12s for a while and had started to think the grass was greener with double nationals, hence the split. The 14x12s can start with comb in nucs and transfer to full size once they’ve got going.