I know the image sucks, but it’s a quick drawing of a top view, middle is the head and the other two balls are shoulders, I have this friend who’s short and said her bideltoid is 50cm, which is quite high for someone with her height (166cm), not even an 190cm bodybuilder has this bideltoid, when I ask how she measures, it was clear why the number got so right, she uses the measure curved around her back, making an arch, which increases the measurements a lot, while from what I heard the measures were always straight lines with a ruler like thing