The engine is pulling a S.E.5a WW1 biplane, the first test was done with wing assembled.
Lately I have done a second test with out wings, same engine, same prop but the fishing scale is now reading 8.4 pounds of thrust. Then I believe that sticking with the results of the Pe Reivers original chart is not a bad idea.
The fuse with out wings represents a cleaner air flow but the big radiator at front and weight of the fuse represents a lot of drag which can not be determinated in an uniform equation because the shapes of all different airplanes so there is no way to say that this method is close to the real facts, but it is a good method to have an idea when testing different props. that is why I will build my test stand with the fisher scale fashion.