I have two Custom 22's. a 2004, and a 2008. The '08 is considerably lighter than the '04. Also if I knock on the back the pitch sounds more hollow in the center of the back versus the edge or bottom portion. Is there a chance it's weight relieved?

http://imageshack.us/photo/my-images/715/imagecdg.jpg

It's not letting me add this photo to the post. Might be the iPad.