Good news for IPv6 users!!!
With the introduction of PMS 0.9.12.5 ( see https://forums.plex.tv/discussion/comment/978927/#Comment_978927 ) the Plex team supports custom URLs. In combination with port mapping services this works just fine. I successfully tested PlexWeb and PHT. The iOS App did not find the server yet, perhaps there needs to be another update for that app.
