Just noticed that there is now the option of buying a "large" QuickFit 20 band for the Fenix 6S on the Garmin website.
https://buy.garmin.com/en-GB/GB/p/552261/pn/010-12942-00
It only comes in black.
Could be useful for guys who wear the Fenix 6S and would like a bit more slack and the option of having the rubber retaining hoop on the side of their wrist instead of the underside, which might be more comfortable.