slickbrick there is a couple of ways to do this assuming you have a sinsplus for your versions/expansions of sins,
the simplest way is to use the weighted and random planet types(this method works with all expansions and the maps work weather or not the other people using your maps have the same mods, so I think this is the slightly better method)
the other way that I know is to find a copy sins+ galaxyforge addon so that you can add particular planet types in paticular locations
I do not know which version of sins/entrenchment you have, but would suggest looking in the 7 deadly sins thread for more info as uzii bequethed the sins+ to 7 deadly sins a while ago
harpo
