What Happened: Nozzle blew out again just like the last launch attempt!
Cause: I was wrong in my assumption on the last page of the nozzle being the problem. The problem as James Yawn kindly pointed out to me, was that my grain configuration was far to extreme. It was generating an initial Kn ratio of 304, which translates to about 1200psi on the motor body! This is far to much for a paper tube and so it burst. Howevor as is the case at these speeds (higher speed gasses such as those in flash don't show this effect as much) the gas will find the weakest point. Well the nozzle, although perfectly strong was still weaker than a cardboard tube and the PVC tube that it fits snugly in so it blew the nozzle out.
The photo wasn't interesting enough to bother posting....