Jamie/Draugnar, I actually like your proposal. Of course, we considered it, but we thought it to be rather unfair for the "outsider". Now, if someone is fully aware of the situation and still wants to join, that's fine and could make the game in fact more interesting. Maybe someone is indeed willing to join. But no Top10 player, if possible ;-) And he should be able to negotiate in German. We'll think about it and I'll post to the forum if we need a 7th player.
Ghostmaker, thanks for your help, I already replied to your mail. The procedure seems rather cumbersome to get through for a player who just joined and is not familiar with the site anyway, and I'm afraid it might cause suspicion from players who don't fully understand why we are actually forced to do that.
Actually, I have a test installation of phpdiplomacy 0.81 on one of my machines and we could even play a 6-player game there. But it's not well tested and I would be the admin with full access to the DB, so again someone might get suspicious...