http://www.minecraftforum.net/topic/310298-100robintons-mods/#CubicChunks www.youtube.com/watch?v=XyW0kDuKLUg
not possible for a server. anything above 256 blocks in height begins to kill the sever. It would also require re-writing portions of the server to be efficient. nice idea, but not possible at this time.