Maybe your advice isn't very good?

Since the magazine article wasn't really trying to sell me engine soft mounts, I'll stick with the magazine article thank you.

If in doubt, put the meter on the plane and resist the movement by hand on say both aileron servos. Measure the difference. You'll get an instantaneous change which is represented by a short lived increase in load.

In use servos have a relatively light duty cycle... overall the difference is not as much as you seem to be making it out to be when calculating flight pack times.

So performing the test as indicated and backing off from the total measured as I said is certainly a good way to test. You merely never run the pack to the full time...

As I alluded just as if you were timing your plane for glow fuel use.

If on the ground you can run the plane for 20 minutes at 90% throttle, then you are CERTAINLY safe setting your timer for say 15 minutes.

Common sense.