I'm at a 5, and only because I've implemented a lot of guardrails, am using a typed functional language with no nulls, TDD red/green, and a good amount of time spent spec'ing. No way I'd be comfortable enough this high with a dynamic language.

I could probably get to a 7 with some additional tooling and a second max 20 account, but I care too much about the product I'm building right now. Maybe for something I cared less about.

IMO if you're going 7+, you might as well just pick a statically typed and very safe (small surface area) language anyways, since you won't be coding yourself.