I was wondering last night if I was a bit premature in hiving that weak nuc yesterday, but it just looked so much more healthy with lots of capped and uncapped brood and honey stores than when I put it in the 4 frame nuc, they had no room to expand at all! In 4-5 days they'd be boiling out of there- I figured it was time.
For little nuc the room is better to be flexible. If you devide Langstroth box with middle wall, you have 5 frame space, When brood emerge out, just move wall and give them foundations one or two. When it is summer, they do not store honey but they spend it for building. Little nuc is very eager to build foundations if queen needs them. In cold hive it is difficult to build wax. But bees make wild hives in strange places.