I use them as well JB and can endorse their usefulness.
I also use them to monitor batteries during discharge /charge cycles which help to pep up and prolong the life of rechargeables. Especially NiMh and LiPo.
Cheers, Doug😎

A short video of load testing some new 3300mah LiPos (35C and 60C) to make sure the props are not overloading the batteries, ESCs or motors. In this case, the amps are only at 50% of the max capability static, which means in the air they will be less (unloaded). With boats, testing should be done in the water, (static) as there is no load to speak of with a boat prop in air (unlike a plane) When the boat is running free, it will unload. If you set the amps to say 80% of max static, it will give a good safety margin. A meter like the one shown, is a must for boats using Lithium batteries.

These testers will help you avoid smoke leaks from your batteries, wiring and ESCs. I've used these testers for 13yrs, and never had a problem with LiPo powered planes or boats.

JB