Awesome, April! I've noticed the same thing happening with me. My shoulder width has shrunk by almost 4" and my neck has shrunk by 3.5" as well. Really, at this point, the only things that are on the large side for me are my trapezius and pectoral muscles that are leftover from extensive weight training. When I go running though, I see plenty of other women with the same thing so I consider myself in the female range. It's just a matter of not wanting to look that way from a normal body image standpoint as opposed to anything dysphoric. When I started, I honestly never thought I would ever be at this point, where I am happy with my shoulder and neck size.
I used to have this bad habit of putting my elbow on the window sill while driving. The other day, I realized I wasn't doing that anymore. I tried to replicate that position just for fun, but I couldn't do it; my elbow was missing the sill by about 2 inches! When I started on Susan's, I read a lot of posts that said that shoulder width doesn't change on HRT and that made me really sad. I'm glad you made this post, April, because new transitioners should know that it is possible and that there is no need to feel the way I did.