The pdf I used earlier explains the resistor type and time, 5ohm 10W ceramic. Not kept on long enough for heat to be an issue.

A wattmeter/voltmeter+ampmeter can only measure within good accuracy a pure sin wave - at least, I don't have a model that can sample wave energy and average it. The signal was read using a digital oscilloscope to ensure the amp wasn't overloading and distorting the signal. The amp I use to boost the signal generator is a class A/B 100W. I also use a class D 100W and get the same figures.

I hope your man isn't using the built in li-ions to skew the output results as the German translation is not clear. This would be very unfair.