Have been digging around in the archives for a while and there is not much info on this subject.
Consenus seems to be around 24 inches, but that big powerfull surfers with big feet can go much wider until you can't paddle the board effciently.
My question is this at what width do you start to see the actual width of the board start to slow it down?
I still have not to this day seen a fast SUP in small weak waves. Maybe this is due to the amount of rocker, but at some point the drag created by such a large wetted area start to slow the thing down?
Longer narrower boards with minnum rocker IMHO tend to look faster then SUP's in weak waves.