The weight of the rider doesn't have anything to do with it. The ideal shift points are the same for all riders, as everyone wants to maximize the power to the wheel. Note that these are numbers for max acceleration. It's an academic exercise for the most part. If you're happy shifting lower, then shift lower! If you want to see how high the engine can go, just rev it out. Grab second gear, and hold the thing to redline (60kmph+). Eventually it will just stop accelerating, as there is a rev limiter to protect the engine. You can hold it wide-open against the limiter for as long as you want with no worry about damaging the engine, although I'm sure your ears and butt will have you back off soon.