The vast majority of compound nouns form their plurals by adding s to the principal word in the compound. Examples: He now has two mothers-in-law. (plural of mother-in-law) They were visited by the Knights Templar. (plural of Knight Templar) It was a sight to see four lieutenant generals fight it out at the table. (plural of lieutenant general) Jerry had attended over a dozen courts-martial. (plural of court-martial / also, see third example below) No Principal Word? When there is no obvious principal word, add s (or es) to the end of the compound. Forget-me-nots make a wonderful present. (plural of forget-me-not) Pack two toothbrushes. (plural of toothbrush) Jerry had attended over a dozen court-martials. (There is ambiguity about the principal word in court-martial. Therefore, through common usage of both, courts-martial and court-martials are acceptable.)

Yes, I think you can. Here's a site I found about compound words, it might help you, I hope! http://grammar.ccc.commnet.edu/grammar/compounds.htm

Thanks a lot! All of your answers are helpful! :)

Yes, you can.