Extending the Pier User Data Model

I'm trying to find the best way to add a collection into the Pier user data model. I located this advice: "For adding properties like first name, last name and email to a user the easiest way is to add some Magritte descriptions to PUUser.Add your new description methods to a new category called something like *myproject-usermodel so it won't be overwritten when you load new versions of Pier-Unix-Security from Monticello (the star at the beginning of the name is essential)." Can one do this without also adding instance vars in the PUUser class? And If not, wouldn't those instance vars be overwritten when you load new versions of Pier-Unix-Security? In my case it also applies to PUUser>>initialize, which initializes my empty collection. Won't that be overwritten? Am I going about this the wrong way?