Put the brood frames on the wall of the hive. Might not work in a nuc with a good laying queen, but it's usually the last place used for brood. Remove when brood hatches.
Or else find where the frames are too big and maybe give them a quick shave with a chisel or dremel.
A double 8 framer is really not much larger than a 10 framer. You could put in a board to reduce the space in the 10 framer as it sounded like the big frames fitted into the 10 framer?
Too much space might not just cause cold trouble, but also sets the bees back. They don't seem to build as quickly, as if the prospect of filling lots of empty frames is too daunting and they just give up. It is also not good to have too many unprotected frames. When bees cover frames it is harder for shb and wax moth to take over. If you do have extra frames that bees are not covering, maybe put in plain foundation which is not appetising to those pests, until the numbers increase. Keep the brood and built up frames together, and they will slowly work outwards when they are ready. If you truly are having cold weather now, then you should move them up north :)