When I waddle into Wal-Mart, wheezing and on the brink of death, I go for the scooty-puffs, but just the normal sized ones.  Granted, I hang over a little bit on either side, but I can still balance on the seat just fine.  I can't IMAGINE how big you'd have to be to need one of the extra wide scooters.  THOSE are the real fat people.