I split the difference on the 26.8 and the 27.2 as possible CP locations, and gave it a 27 as the source to measure from. I loaded my repaired Hydra VII with (7) C6-7's and balanced the rocket using the original payload section. The rocket balanced (CG) a marginal 1.5" from the CP, which is less then the 1 caliber needed. Since the BT dia. is 1.6" roughly this is where the instability came in to play.
Fix: (2) one ounce lead fishing weights attached to the eye hook in the payload section will fix the problem. This will just clear the 1 bodytube caliber needed for straight flight of the Hydra VII. For a little security, I will add 1 more one ounce lead weight.