You are right, my template is off, but I will have to clarify this. However it seems to work out when it checks the header ID, and block size. The other 9 bytes may have been held for future development. I have to tramp through the history for this.

For the third field I use "H4" because the data returned properly. I don't believe the number of blocks will never exceed 8 but I guess I should use the proper form anyway.

Thanks for the tip on H*, this is my first attempt at Pack and unpack so my steps are a little unsteady still.