I agree that is a great find. When I was teaching in a single engine airplane, our Dash-1 had us fly a few knots above best glide (the theory was, I believe, to keep us at a slightly better position in the ejection envelope in case the glide to landing didn't work out so well... not really a factor in most GA planes!).
Anyway, students would frequently slow down to L/D max when it looked like they were not going to quite make the field to "stretch out the glide." Of course, usually the reason they were not going to make the field was due to a headwind, and I sometimes had the hardest time convincing them that faster than L/D max actually gave a better glide range given the wind conditions.
I finally settled on this example: L/D max speed=105 knots (assume IAS=TAS, which is a good approximation at low altitude and low airspeed). Now imagine you are in a 105 knot headwind. What's the glide distance? 0 of course.
What happens at 106 or 107 knots? Well, at least you move forward a little, even if it is a couple of feet. Glide distance improved by flying OFF of L/D max.
Once they get that concept the rest is gravy.
