Oh, I have done my own test indeed. I have an air boat and found my own calculations to be much different than what I have read. for example, the boat has a top speed of 44-48 mph with an APC 11x3. When using a 11x6 it will only travel around 36 mph. When usung a 10x6 it does around 33 mph. Used the radar gun out of my patrol vehicle - I know it's right; they have to be calabrated annually.

Even did calculations with many props using fixed numbers of effiiciency, ie 50, 60,70, and 80%. The only thing left is to get a tension scale and physically test many variations of props...