Thanks for the reply, Ingo.
I found the wiki pages about subclassing Member and also the DataObjectDecorator.
The trouble with the second post is that it appears to affect every instance of the class that is decorated.
Here is my problem in more detail. In a modelling agency site, I have two member types: Model and Client.
Models need to have things like gender, height, eye colour and so on. Clients need to have business information, multiple contacts and so on. They all need to be able to login and modify their information online.
My guess is to create two classes ModelMember and ClientMember that both extend Member and then create specific pages to manage the registration and profile management etc. I assume that things like ForumRole will still work as they will decorate the base class Member, which will flood down to the subclasses?
Is there a better way of achieving this?