Ow. My brain hurts. And I still can't manage to grasp the general rule about making things plural (or possessive) if the word or name ends in "s" - like, just for instance:

This stuff belongs to Angus. Thus, is this stuff Angus' or Angus's or the-stuff-of-Angus?

There is more than one Angus in a room: Anguses? Angusi?

Apostrophes, alas, are not my friend.