TerrainPage vs TerrainBlock

I'm creating a rectangular terrain, which is pretty far from square. That is to say, 50x200 or maybe even 50x400. So far I have used a TerrainBlock for this, but it means everything (heightmap, texture) gets stretched a lot along one axis. Will a TerrainPage give me any benefits here, or will that give me the same problems (just rendering slightly faster because of possible culling)?

Update: Let me simplify the question, since nobody seems to answer this… Is it possible to have a TerrainPage that does not consist of NxN TerrainBlocks, but of NxM TerrainBlocks? (where N!=M obviously). if not, then how can I get rid of the stretch deformations in an 'oddly' shaped terrain (i.e. non-square)?

I don't know why but there's no standard support for rectangular terrains.