Note that, in the case of opposing mirror plates, the surface, or crustal magnetic field ( the magnetic striping which runs parallel on the original shields when they are re-assembled ) also mirrors itself.

The world's crustal magnetism actually mirrors itself in all directions. I don't believe this would be the case if the continents were moving on a constant diameter. I believe this mirroring of crustal magnetism is related to influence of the original impact on 'Convection', the currents of movement in the Earth's interior which are believed to drive the continents movements, and generate the Earth's general magnetic field. This will be addressed in future drafts ( see Full Sequence and Notes )