The Chicago Manual of Style says that “hyphenated and open compounds are regularly made plural by the addition of the plural inflection to the element that is subject to the change in number” and gives as examples “fathers-in-law,” “sergeants-in-arms,” “doctors of philosophy,” “and courts-martial” (196). The NYPL Writer’s Guide puts it this way: “the most significant word — generally the noun — takes the plural form. The significant word may be at the beginning, middle, or end of the term” (396). And then we get examples such as “attorneys at law,” “bills of fare,” chiefs of staff,” notaries public,” assistant attorneys general,” “higher-ups,” “also-rans,” and “go-betweens.”

Ok… so i’m a geek.. but I found the descriptions useful…

Anyway – as you were!