For me my server shows up twice on the serverlist. That's how I know it is visible to everyone. Is there anything unusual about this?
I wouldn't worry about it. I believe that happens sometimes because the server browser populates the list from dplogin.com and your LAN (Local area network). Other people can't browse your LAN, so they will only see one entry.
It shouldn't matter which one you connect to.
As a side note: This guide has been copied to the wiki.
http://wiki.digitalpaint.org/doku.php?id=port-forwarding_guide
