So what are the odds that all three motors from a pack or E9-6s will CATO?  Pretty good apparently... Rocket got about 30 feet off the rod then BOOM, nozzle blown out the back and the burning fuel grain blown out the front.  shock cord stayed intact but the motor mount was blown out the back of the rocket with the motor firmly seated inside and the body tube suffered significant damage.  Loss.  The worst part is that I have two more packs of E9-6s that I bought from the same vendor at the same time.  Think I'll have to write those off.