Interesting thread. I had to try some testing. I have a Turbo Dyno.
17.5 motor with Tekin RS speed control.
Dyno set to Amps
Voltage at 5V
I pulled the speedo out of my 1/12 scale and just put it right onto the dyno with the motor. On the first test, it wouldn't get to the high amp settings. It would go to about 17.5A and then stay there. I figured it was the 16awg wire so I changed it to 12awg. Didn't make that much difference. There were slight wattage differences but that was expected on the low end. I bumped the voltage to 7V. This cured the bottom end reading. Without getting too much into the dyno programming, I figured that the 17.5 motor wasn't turning enough rpm to let the dyno read the bottom values.
Played with boost on the speed control. All indications show that no boost is the most efficient and produces the most overall power. High boost mostly affects the very bottom load setting. In stock racing, that bottom load value rairly gets used in my experience.
After reading this thread, I found a new use in what I thought was a paper weight on my R/C bench.
Maybe CE will revive the Turbo Dyno with a brushless controler built in. I'm sure there's plenty of room inside that big case.