Only two of my colonies are still on more than a single 14 x 12 brood, on which they will eventually over-winter without further feed or other interference (hopefully) until warmer weather in the spring allows the first quick (hopefully, again) inspection.
One is too big for the single brood at present and the other is one I forgot had a double brood box, and I need to check the bottom box soonest.
It is now far too late to expect a colony to double in size to accommodate a second brood box. I normally over-wintered on a single brood and a super of stores before I changed to the larger format.
Concentrate on getting them through the winter first and allow/encourage them to expand in the springtime. I would suggest your first objective next year is to expand to two colonies, if that is an option, as two colonies are generally easier to manage than a single (test frames, balancing brood and stores, increase, etc - all with not so much extra inspection time taken).
How many frames is your colony occupying/using? If not a full box it may be advantageous to replace an outer empty frame with an insulated dummy/divider, if they do not completely fill the box with stores.
Regards, RAB