Vista - Syndication Extension Elements Sample (Orcas Beta 1)

Are there any examples of how to create and consume feeds that contain
extension elements?

I have managed to create a feed with extensions after some trial and error
but I'm not convinced I'm doing it 'the right way'. Also I've not been able
to consume a feed that contains extensions such that it deserialises into the
correct objects (at the moment it just deserialises them into generic
ExtensionElements). I can't see a way to tell the serialiser how to map
namespaces and/or elements to classes.

I have downloaded the Oracs samples but can't find anything there. Some
brief sample code would be much appreciated if there is nothing else out
there.

Thanks,
Phil