I think it is very unlikely that they will draw comb until the weather warms up. They will most like store the syrup away in the two drawn boxes, and if you continue to feed, they very well may become sugar honey bound.
I know there was a post the other day that said you couldn't feed too much, but I disagree. If there is no natural flow yet, and they continue to take syrup, they can become bound. It is very important you keep an eye on them while you feed. If they become bound, you are just reducing your bees when there is a nectar flow and you need them the most.
Rob you totally right. When bees get food ouside, it speed up brood as much as hive can keep them warm. There is no use to feed them sugar all the time.
I have speeded my hives 12 years with pollen patty. I continue it 1,5 months. Now, when I took into use terrarium heaters I can see that the temperature of hive is minimum factor in brood rearing. With protein and with warming hive developes 3 times faster, but only the big ones, one box or stronger. Little ones I kick up with brood frames which I take from biggest hives.
You have non insulated boxes and surely cold boxes hinders the growth of colony.
When last summer it was 2 weeks cold and bees cannot go out, the brood area dropped to half even if I had protein feeding and warming all the time. When I took my 4 largest hive outer pastures and without warming and but I feeded them, brood rearing stopped very badly. Some reported that in their hives 90% of brood vanished.
Why I am telling this. To get optimal spring development bees need warm, protein food (pollen), inspiration from flowers and a lot of feeder bees.
With this hive is ready to get early honey yield. Many are angry with me because they do not want to work so much with bees. They say here: THIS IS UNNATURAL!. Of course it is, and it must be. So you have difference with skill and smaller skill.
I give now lessons concerning spring feeding and the name of lesson is "two fold honey with same hives". But that is not nice; hard work to sell honey.
And to learn this had taken from mee 12 years it is not easy to others. Don't be astonishes if it does not work at once.
Also you can see that there are many advices on the contrary of this, but I just told my experiences.
But to get 200 lbs honey per hive, it is not easy. To get 60 lbs, you need to do almost nothing. To keep 10 or 30 hives and you get same volume of honey, there is also big difference.