Happy New Year!
I almost went with double wall PC but couldn't let myself part with so much light. I get plenty of direct north light May thru July, guess because I'm south of you as the sun swings north around the solstice. Single digit winter nights are very rare for us.
Day is a good avocado but gets really big. I also have Brogdon which gets big. Am using Bonzi (a PGR) to try to cut down on the size, and pruning. You'd be better off with a dwarf like Gwen which has short internodes and gets to around 10'. Have given some of my citrus 3 haircuts lately. Some like the Mexican lime are exploding with blossoms and new foliage. They really like the RootBuilder pots.