Hey, dodge the whole issue of spherical surfaces and projections and distortions -- one group that's done JUST what you refer to - they periodically just expand - is the French geofiction game/community of Alliance. I link to them in this thread. In short - if you use a Niven ringworld or something like the Halo setting, you can expand to your heart's content, maintain effectively a flat earth, and never run out of space.

Starting from some center, and radially expanding as the original territories get mostly filled with participants *does* avoid the perennial problem of collaborative geofiction - the difficulty of imagining *your* space when initially lacking neighbors.

204 participants? I'm impressed.