Should a two-word noun that modifies be hyphenated?

There is a probable duplicate, but I've never seen this (doubtless nonce) compound secondary-modifier (adjective modifier, traditionally adverb) before.

Fibonacci∞spiral∞attractive.

Where if anywhere does one hyphenate?

Looking for similar strings that are idiomatic, we find

• drop-dead gorgeous and arguably
• lead-pipe cinch but
• stone cold sober as well as stone-cold sober.

The latter is probably so idiomatic that a hyphen is felt to be unnecessary clutter. Practice may also vary with position of modifier (prenominal or predicative).

With the nonce candidate here, there is obviously a possibility of confusion, one factor being the unusual reference (a Fibonacci spiral). (Actually, the golden spiral looks more perfect ... I am assuming that the meaning here is supposed to be very, very rather than rugged, angular). To show that this is a cohesive unit (rather than spiral attractive), the gluing effect of a hyphen is best employed. Also, scare-italics for a nonce usage. And a clue to the intended meaning.

He's Fibonacci-spiral attractive.