Hibernate version: 3.0.5

From the Hibernate Toolset document at (http://www.hibernate.org/hib_docs/refer ... guide.html) regarding the 'extends' meta tag:
"class the class should extend (ignored for subclasses)"

... why ignored for subclasses? Is there something wrong with having it extend a different class than what's mapped in hbm and having that non-mapped superclass extend the mapped superclass?

MappedClassA
|
NonMappedCLassB
|
MappedSubclassC

The reason I ask is that, naturally, I want to implement some custom behavior for my subclasses but want to continue to use hbm2java... and keep my persistence bean properties seperate from the business logic.

I can probably work around the hbm2java thing, but I'm wondering if hibernate will have some problem with me doing that sort of structure.

Thoughts?