I don't know if this question is still relevant, but I'm still answering to potentially help others.
The full documentation of the OP2/Op4 format can be found in the Nastran DMAP programmers guide (https://simcompanion.mscsoftware.com/infocenter/index?page=content&id=DOC11149&).
I don't know if this question is still relevant, but I'm still answering to potentially help others.
The full documentation of the OP2/Op4 format can be found in the Nastran DMAP programmers guide (https://simcompanion.mscsoftware.com/infocenter/index?page=content&id=DOC11149&).