I am working on a very similar planet generation project, except my code is C++/OpenGL with an eye towards cross platform support. Once the code is stable enough, I plan to go open source and release the terrain generator as a separate project from my game engine.
Should you choose not to release your source code, I would be very interested in comparing code bases in the near future. Let me know if you are willing.
Also, what is the other 'visibility method culling' you were referring to that's used in addition to occlusion culling?