Russell, I'm in OKC and have simular weather as you but somewhat colder in the winter. I think you are babying your temperate trees too much. We got down to 19 last week with 7 inches of snow and todays high was 73, it's like this every year. I keep my chinese elm, red maple, pines and junipers outside all year long with no problems. I haven't grown the hinoki cypress but it should like simular conditions as the pine. The main thing you want to prevent is strong winds blowing on your trees when the rootball is frozen. Just mulch the pots in and provide a wind block and they should do fine.

Tony