I played around a bit with this for both a SM F-18 and SM F-16 using the CGCalc spreadsheet from the link above and it looks like the elevator rods are very close to, just behind, the AC, aerodynamic center. I am getting centers of 6.88" and 7.25" respectively. The elevator rods are maybe 1/4" behind that at most. So if I can trust I did it right that's looking pretty decent for a pivot position would you guys agree? Certainly these a proven designs that have stood the test of time but it is interesting to look at this in detail.