You could try using a larger heightmap to decrease bumps when rendered (especially if you're resizing the terrain larger in the Map Maker). Contrary to popular belief, you can make heightmaps larger than 513x513. However, they MUST be a power of two plus one, hence (512 + 1, 512 + 1), (1024 + 1, 1024 +1), (2048 + 1, 2048 + 1), et cetra. Note that it will also increase load times significantly, by about the same factor of a power of two used when loading the heightmap and generating terrain.