Proper way to map inverse domain?

I’m still working really hard on both my solutions, and have a question on the inverse domain in an nhibernate setting.

I know I need to set instance.Inverse in HasManyConvention, but I am uncertain as to how I should set Cascade for both the HasMany and Reference conventions. Could somebody give me the lowdown on this?

Also, would this scenario then allow me to insert, update, and delete entities on their own terms, without resorting to AddThis and FindThat and RemoveOther methods?

In other words, I want to provide a repository for each entity type and do this:

forumObj = new Forum(title, categoryObj);
forumRepository.Insert(forumObj);

Rather than:

forumObj = new Forum(title);
category.AddForum(forumObj);
categoryRepository.Update(categoryObj);

Thanks in advance.