Downsize Public Folders for Migration to Office 365

To migrate public folders, I have been following this link: http://technet.microsoft.com/en-us/library/jj983799%28v=exchg.150%29.aspx

However, this customer's public folders are exceeding well over 50GB. There are contacts and a calendar. I am looking for assistance/advice on downsizing public folders for migrating to Office 365.

Exchange 2007

Server: Windows Server 2008 Standard