Originally Posted by DocHolliday
Flusser's "Dressing the Man" has a section on shoulder size/head shape you might find helpful.
Indeed. He suggests padding on the shoulders, but only horizontally. He also suggests that the shoulders be sloped (for, unsaid, illusion of width). In the section, Flusser hardly discusses other details such as neck length. (Built-up shoulders might be helpful for someone with a long neck and not just the very sloped shoulders that he mentions.)
Also, regardless of the jacket construction, colors and patterns of the tie (or, without a tie, shirt) worn can affect perceived head-shoulder proportions. Essentially, slightly distracting from a large head will shrink it.