On a KSP video I watch once. The person said that Kerban Geo orbit is 2,869,000 meters. I put a satellite at that altitude and it did seem to stay in place. The game crashed and I had to reload it so I could not track it for a long period of time.
Here are a few pictures of China's space station and how they plan to enlarge it. I haven't mastered docking yet, so maybe someone else would like to give it a try. The station today. http://www.chinadaily.com.cn/china/images/2011tiangong/attachement/jpg/site1/20110929/00221917dead0fee194911.jpg Docking http://www.space.com/images/i/13076/i02/shenzhou-tiangong-china-space-docking-111102c-02.jpg?1320269231 The competed station. http://interspacenews.com/Portals/3/Articles/images/20110929_china%20space%20station2.jpg Good Luck!