Paul, I will try to post some pics when I get a chance to take some. It is mostly trial and error. The tip profile is like a APC in shape, and the blades are thinned. I start with balancing the stock prop. Then re-shape the tip, and re-balance. Then thin the leading edge, and re-balance. Then the same for the trailing edge. Sand and seal with thin CA, and balance. Now flight test. I don't believe in tach readings the proof is in the flying, and throttle response. The prop that Jeff had started as a 12x4 Zinger. It was a little to much for my HP.40. I use a 11x4 for it. All work can be done with a sanding block with 80 grit paper, then smooth with 220 or finer. You can also try a Dremel with a sanding drum, but it is easier to mess things up. Tom