I recommend using PNP-Terrain Creator, and after creating the entire large world, export it as multiple height files. Use the 3 texture shader, but each zone can have 3 different ones from the one next to it. This way, zone 1 can have rock, gravel and sand where zone 2 right next to it can have grass, asphalt and metal.
If you are interested, check these videos out, you will cheat the system with shaders which will speed up your game and not reduce your FPS, yet give you an almost endless terrain system if done right.
http://www.garrettwademan.com/3dgs/zoned_terrain/videos.zip