I'm not familiar with the Majipoor series but I would think that anythingn as "small" as a mountain could be most accurately depicted with something simple like an equirectangular projection. After all, you're not dealing with the problem of trying to flatten a sphere. If depicting the different elevations was imperative than a topographical map (in equirectangular projection) would be the ticket. Remember that all maps warp a sphere, but you''re not dealing with a sphere, so applying another projection would distort the mountain.