I've been reading about the Impact failures and find it interesting. I have not had a composite pattern plane, so I'm speaking only from what I've read here.

This reminds me a little of a failure state in the Army OH-58A & C helicopters. These are versions of the Bell Jetranger. The failure mode is called critical tailboom dynamic mode. The tailboom would buckle at a certain spot during vibrations in autorotations. Basically, a terrible vibration would be introduced at the rotor head and then cause the transmission to start oscillating in the pylon mounts. The vibrations would travel down the tailboom in a sine wave. Once they reached the end of the tail boom (with vertical fin and horizontal stabilizer) the vibration wave would start a return towards the nose. This would meet the next wave from the transmission, and the buckling would occur at that spot.

I'm wondering if vibrations aren't flexing the fuselage in a similar way. They do damage. We would look for 'oil canning' on the panels to find small buckles in the sheet metal. Someone mentioned a nose ring set up doing well, without problems.

Or, maybe the tail feathers are flexing the fuselage and causing stress failures.