A large terrain for background and smaller detailed terrain placed on top? Is this the right idea?

Hello all,

I have a large terrain (8km) that has a full texture map and is based on real-world terrain data. There are two locations where the player will walk around, I have made more detailed terrains (1km) specifically for them which are placed over the large terrain. I will teleport to the two locations, and unload the smaller terrain that isn't being used.

Is this a correct method? I don't want to cause any future pain. Thanks!



More details:
Large Terrain:

Smaller Terrains: