Grammar Geek, I think that your interpretation is the correct one. When you mention a protocol officer, does this mean that there is not a gramatical answer and it instead comes down to tradition or protocol, rather than a definite rule?

Yes, I'm thinking of speaking to two people who hold the same title, and addressing them in a speech.

I have a quick question about plurals. I know that the plural of Attorney General is Attorneys General, and Secretary of State is Secretaries of State, but what of Madam Administrator or Madam Secretary? Would they be Madams Administrator and