Terrain matrix 8*8

Hi all i've searched around on the forums but i haven't found anything. recently, i've experienced the 65.536 colliders limitation in physix engine, so i can't have all the details that i want in my game. Than I've thought "why not making more terrains and only render the closer to the player?" In this way, the player can choose how many terrains render in the game (for example: this terrain, the terrain on the left, on the right, ahead, backwards and the terrains on the angles, ore more), using this technique i can only apply colliders to the trees and details that are currently shown, am i right? Than i've split my heightmap in a 8x8 matrix (6x6 can probably works, but 8x8 is more... i don't know, i simply like 8x8 :) ), but when i try to apply different heightmaps on different terrains... well, it doesn't work. i've seen the setNeigbors function, but i can't (as before) use multiple heightmaps... Any idea? Thanks for help and sorry for my bad English. Z171