Amazing, Rod! I accidentally posted a completely forgotten set scaled to the 7.5" inner diameter of a Model A10 Aerobie. How did you deduce the 7.5" value with enough conviction to spend that much effort solving it? Without revealing too much of your solution, I also eagerly ask: How many different partial solution candidates did you have to test by hand? Were you able to determine that the solution is unique? How would you describe the "nice symmetry" you found? --Bill Gosper