First, welcome. Now, for your lovely plant. These do some slight growing in the winter but nothing to write home about. Spring is the time. Size isn't the issue. You have bare trunk and a head of leaves with, what appears to be, a bifurcation. In the spring, I would have no problem cutting the head off about 2 full leaf scars down. Allow the head to callous and replant in the same pot. I would possibly replace the mix with something more gritty by adding some perlite and make sure your container has drainage or if you have a pot in a pot, raise the inner pot on some stones so it doesn't sit in water. The end result is you will have "three" stems growing and it will, with time, look great!

Thanks for your response. I really appreciate the clarity.

All of my pots are drilled - a post about drilling vintage pots was what first brought me to gardenweb. The mix is a cactus soil, but I'll switch it over as you suggest in Spring.

Thanks again! Hope everyone has a nice weekend.