Having them below with an empty box on top is not a good thing. Trapped heat will be one of the best things they have right now. Combine them into one box.
Call C.O. Nolt and sons out of Lancaster Pa. 717-397-0751 Ask if they deliver to any Bakeries or supermarkets over in your direction. What your looking for is a product made by Dawn foods. It is a 50 pound block of Bes-Fond fondant. (about $38.50) You could also check on the Dawn foods website or check your local telephone book for bakery supply places.
I have taken bees out of pumpkins with no honey stores. I take half the block, and place 25 pounds directly on the inner cover. (this is why you knock them down to one box and leave them at the inner cover hole) Then you place an empty box around that, and put the top on.
It is not the cheapest way of feeding, but it keeps the moisture down inside the hive which is a killer in cold weather, and what you will get with syrup feeding. I have kept good numbers of light hives alive all winter this way.
If you or anyone you know is attending the Pa. state bee association meeting in Nov. let me know. I can take along a block with me. You can get away with some syrup feeding till then, but do not suggest you use this method much longer after that.