Bill, thanks for the run on comments. Chris thanks for the clarification about who else is affected.

Bengt, my guess is, and I am not an engineer, that you are correct. The more flexible prop interactions in other types are placing less of a bending moment on the shaft. Additionally, the current prop shaft is already at risk because it has a half round radius cut in it circumferentially, which apparently has been a point of failure. Steve Leonard et.al. have discussed these issue in depth in other threads, related to the first group of failures.

The rubber prop attachment apparently is an attempt to make this situation more like the types (Ventus CM) which are not showing failure.

Regardless, I still stand by my original statements which I think are self apparent.