Look at my map10a in the archive. You only have to patch for nexus style planets, and away you go with over 7000 to choose from. I advise a ten planet start so that the average number nexus style is the same for all players. Have at least 9 players, one to be the nexus holder and be given a 40 turn truce before you attack. Unless you mod the central system the nexus holder needs to be a Co2 Gas Giant race.....

Hint - unless you disable events, the nexus holder MUST evacuate out to the fringes in a long game, because with 16 stars per system and many of them unstable the chance of a system blowing up regularly is high. OTOH the holder has the pick of the quadrant to choose from with those one way warp points, and only has to defend 4 warp points to hold the inner ring of 1 + 14.