Extended bodies are heavily used on larger mayflies. There are no reasons why you can’t use them all the way down to size 16. The only thing to remember is to find a chenille that’s slender enough to imitate the natural.
André Brun is a Norwegian that is heavily promoting this fly. He also has a chenille that work well down to size 14. If you wanna tie smaller use the variant I’ve used for the Ignita Spinner.
You can tie the fly both with a poly wing or a CdC. Just make sure you’ll get the profile right.