Plurals

Q. My question refers to the plural use of acronyms and initialisms. As I have always understood it, the acronym or initialism can be pluralized only if the last letter indicates the plural item. So MOU (memorandum/memoranda of understanding) cannot become MOUs, but ICT can become ICTs (information and communication technologies). I run into this problem a lot with the initialism RFP (request for proposals), which people like to pluralize as RFPs to indicate multiple requests. The word proposals is already plural, so it does not make sense to me to add an s to the end of the initialism. What is the correct way to make acronyms or initialisms plural?

A. If you can stop thinking of the spelled-out meaning of the acronym and just treat the acronym itself as a word with its own meaning, you should be able to add that little s without fretting.

[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]