The whole point of this is that hang gliders fly at a speed that is in the same ballpark as windspeeds. Slower, yes, but not by all that much. (A windspeed of 8-12 mph is 1/2 the stall speed of your aircraft!) Slower aircraft need to include the windspeed in their calculations. The faster your aircraft, the less it matters. one can argue about whether a Cesna should worry about it. For a 747, in any reasonable wind, they don't really care. For a hang glider, in any reasonable wind, if you are ignoring wind-speed in deciding your approach speed, you are taking a big risk. And if you are ignoring gust-differential, you are taking a bigger one.
By the way, if there is anyone in the club who knows this, it is Greg Kendall. He helped design and fly the slow-flying solar-electric plane that has been in the news lately. Can anyone say "Stratosphere?"
