you can also make your own wind tunnel - but -that would hardly be a convenient thing for most of us
I use static thrust tests --on gassers --to compare the improvements in torque -using various exhaust setups -etc.
for example --on a Pitts muffler - -say you get 6000 rpm - on a header and muffler 6200 rpm - on a header and tuned can 6400 rpm - etc.,
These all represent big increases in torque- if you had all other things equal - same prop same day etc..
comparing someone elses figures from 1000 miles away is of little value - as they may be at different altitudes and their prop -even same brand may be a couple of hundred different in load -or unblanced , etc..
A GOOD 50 lb Fish scale (new Peizo types) can give accurate readings by having an assistant hold the model - adding power -- then pulling the model back away with the scale and a harness - this way the model is always under control.
For engines ofer 100 , you need a bigger scale -