If the rider is like the guy at work that rides an ST4 it is probably sprung to accommodate his 400+ lb frame.
Geez that's interesting, I worked with a guy who was at least 400 pounds, and last time I saw him, he was riding an ST4. He was working on a road project in the Phillipines and was making big money, so could afford a shiny new Duke, but even though I'm a big fat bugger, I still felt sorry for it..............