Have you thought about getting a new adsense account for those sites which are on different c class IPs? That way, it's less likely you will lose your entire adsense income if they decide to ban one of the accounts.
Get a new name (set up a corporation), a new address that hasn't been used for adsense before, always log in with different IP address, clear your cookies + flash cookies. Make sure your websites on your new adsense account are on different C class IPs and also have different templates and content from those on the first adsense account.