I called customer service last week and the representative had no idea which size. She just read the same internet description that I read before I called.
I called back Monday morning and asked to speak with someone who would know. The operator said that person was busy and she would call me right back as soon as she was free. No one ever called.
Usually, it's pretty easy to tell which size is best when a pouch sheath is offered in two sizes (small or large), but this one could go either way.