Hi,
I'm 6' 2" tall and ~$260 pounds!
So far, I havent had any troubles with my Xootr Swift.
FYI: I did switch the stock stem with a longer one and I did change stock tires with...
Schwable Marathon's (1.75 KevlarGuard Reflex Allround 45-70 PSI)
http://www.xootr.com/xootr/swift/bikes.shtml
Hope this helps.