Pe,

After having heard much about your calculator and seeing it for the first time I had to give it a try, and used my RCIGN1 cnverted G23 engine as the test sample. Using an APC 17 x 6 at 8,900 rpm gave a calculated thrust reading of 13 lbs.

This seems fairly accurate based on the strong flying performance of my 10.3 lb. CG Extra powered by this engine.