Forgot to mention that level in-flight power-in of the motor is 425 Watts, wich comes to approx. 340 Watts power-out.
340 watts is about .46 HP, which is definitely in the ballpark of the shaft horsepower run for IC airplanes. Figure 60% prop efficiency, and you get about .276 drag HP, or about 152 ft-lb/sec. At 80 fps, that's about 1.9 lb of drag, if I did my sums correctly. That is all very close to what we have gotten over the years. Assuming lower efficiency (entirely possible) yields lower drag, of course.
We know the shaft HP very well from many experiments, but what would be very helpful would be to actually measure the drag or in-flight thrust at speed. The best way I can figure is to run the engine, with the baseline setup and the correct static rpm, in a wind tunnel or in the back of a pickup moving at 60 mph or so, and measure the thrust. With the same setup, You could also get the thrust with a constant needle setting over a variety of speeds, which would be the most useful model airplane engineering test I can envision for many reasons. I have been subtly suggesting this test to Frank Williams for about 15 years, since I found out he had a wind tunnel, but so far he hasn't bit.
I suppose an enterprising electric guy could mount his motor on load cells and then fly it, while logging the data. I would be hesitant to do that on an IC engine because of the possibility of it shaking apart, and there's generally no way to log anything.
It would be more difficult to set up a similar test with an airplane, both because you would have to carefully adjust the AoA to give you exactly the right weight, and you can't model the effects of the lines. The latter is probably adequately modeled by LINE II.
Brett