Should medium sized be hyphenated

Answer 1

The rule on this (for compound adjectives) is if one of the adjectives could be confusing to the reader, use a hyphen. For instance, "small-business owner," without the hyphen a person might think the business owner is a small person.

This is a word phrase that doesn't seem to confuse people, so it is up to you. However, I find that people enjoy using hyphens as it simplifies the sentence structure; makes it easier to read.

Generally, it is a good idea to hyphenate when you have a compound adjective in a sentence. I'd do it -- and I'm a marketing editor/proofreader.