XFA, note that the DS is hundreds of KM in diameter. The largest object allowed in FS2 is (correct me if I'm wrong) around 50km. Not to rain on your parade, and kudos if you succeed, but I think it's impossible. Talk to the guys over at The Babylon Project. They have some experience with extremely large objects(the Vorlon Planet-Killer) and the frustration on not being able to get the masterful model into FS2. On the other hand you could create 50km square, detail the surface and let that be the DS, either way even modern systems would have difficulty pushing that many polys.