Thank you Pat. It is good and helpful but I was wanting something more succint. We could use that info in making more of a "bird'd eye" view.
The principles should come before the pedigree. Yes, people need to know some bare bones facts about why the SSPX and its offshoots came into existence.
What's important though is to convince them of the necessity of Tradition - Tradition beyond the indult.
Note that an agreement with Rome would really make it practically impossible to explain to people the principles behind the SSPX's separation from the "official Church" (not the visible Church, of which they have been a part)