RE: V6S: Upgrade from 19" wheels to 20" wheels: Yes or No?
I have the standard 19" Propeller wheel on my V6S, and I'm perfectly happy with them. I live in New England, where the roads are not consistently smooth, so there's no way I'd go with the 20" wheels. But if you live in a part of the country without potholes and frost heaves, then they may be fine. If you'll be tracking it, then the 20" may be good. Not for me, though.
I find the ride to be just about perfect around here with the 19" wheels.