I think that he used the 20x10 @7100 RPM that Diablo-RCU mentioned in his post. He took the 20x10, calculated the load (16,000) then found all the different sized props that would load the engine to 16,000. I believe his graph assumes a peak RPM of 7100 for all props shown on that graph. It would be better if it said at the top of his graph "Brison 2.4 @ 7100 RPM". That's what confused me, I didn't know the RPM was constant across the entire graph.