I have a Med BD in floral chambray. At its narrowest, it looks like 19.5". At the waist, it is about 20".I have a Small BD in one of the newer overdyes (which ran a size bigger). At it's narrowest it is 19.5". The waist is around 20.75"They've been through the wash a few times, but not the dryer. hope that helps.
i'm a little smaller than you, and had the same problem when i sized up to a L. i felt the armholes were very big near the shoulder, so when i lifted up my arms, i felt like i was wearing a wingsuit or something.
They'd were just too big. I sized up 1 because I was afraid of a super slim fit. The fit was okay except the armholes were too big : I felt like I had wings. Managed to score a medium from cncpts and it fit much better.