That is one beautiful specimen Oakland Newbie!
I think since it is such a big specimen already, acclimated to north side facing sun, it has to continue on in similar direction, but outdoors. Cacti do more active gas exchange at night, so being outdoors with lots of air is better for it. It would be nice to be able to move it in a protective overhang during the winter months to keep it cool and dry in case rains come about.
