I made a tutorial / procedure on how to have your full server or VPS and subsequently all sites installed on it, see the real IPs of the visitors. Since Incapsula Support has not published it yet for some reason, I am doing it now here. It is a publicly viewable Google Docs i.e. Google Drive document, so I can update it and you can comment on it etc.
Thread on Incapsula Support Forums: http://support.incapsula.com/entries/22227367-solution-get-visitor-s-real-ips-on-your-dedicated-server-or-vps