Did you include the following "DMCA Notification Statement" listed below or is Google currently using a check box for this? It is required under the law. I submit requested or not to all. Also for $35 you can upload the contents of your site periodically to the Copyright Office in the US.
DMCA Notification Statement
"I have a good faith belief that use of the copyright materials described above on the allegedly infringing web pages is not authorized by the copyright owner, its agent, or the law. I swear under penalty of perjury, that the information in the notification is accurate and that I am the copyright owner or am authorized to act on behalf of the owner of an exclusive right that is allegedly infringed."