-yRNPM6nb76Ul7wI made this video a year or two ago, but it still shows the class pretty well - please excuse the poor gybes and editing.
In terms of weight, it doesn't have as much impact as you might imagine. With a 200L board for all conditions and the choice of either a 6.8 or 7.8m sail, and a centreboard, it is more about racing skills and windsurfing techniques that win races. In the really light wind (less than 10 knots) weight is not important at all, fitness and pumping technique is key. In medium wind (13-17 knots) some of the lighter kids have an advantage as they can plane sooner, but the bigger kids can generally pump harder, so it evens out a little - advantage light kid though. But when it builds ( 18+ knots) the heavier sailors can hold more power and go heaps faster around the course, in terms of speed and upwind/downwind performance.
We have adjustable downhaul and outhaul systems so we can rig up the one sail for the day and adjust it on the fly if required - this is so useful for the newer kids - they hardly ever get stuck in a situation where they cant get home - they just pull on more downhaul. They can de-power enough to sail (and sometimes compete) in up to 40 knots! Yes, thats right, 200L and a 7.8 in 40 knots!

But in terms of actual numbers - I weighed in at 76kg for both of my national titles, this year ill be weighing in closer to 80kg but I will be by far and a way the biggest person to ever sail a techno... Most kids will wont end up weighing more than 70kg, and the kids who are winning the international regatta's are probably 65kg. The important thing to remember is that the techno is purely a learning class - a feed to the RSX. So when you get a bit big for your techno (like me) and you get some good skills up then you don't hang around, you jump onto the RSX and start that pathway. (I have RSX video's on my youtube channel if anyone is interested).