I just cut mine back when it gets too big. Use your judgement, it needs some bulk to be able to keep growing. If it's 12" or more and a branch or few, you could probably take a piece off. I found that at least 3" is a good amount. I usually take about 5" cuttings.
I still can swap some peres cuttings. To warm USA states only.
Roach, I also forgot about the cold. Sending a kratom cutting to Canada would get it frozen for sure.
so how do you care for these cuttings? i just got some in the mail, and am wondering. They require more regular watering than most cacti, right?
how often do you water them indoors during the deep autumn/winter sleep periods?