Ok I congratulate your attempts at this. So many of us have burned this bridge long ago. I myself have created several threads on explaining how to import terrain. Here area few things for you to chew on.
When exporting the terrain from various studios the mesh gets all jacked up. Holes appear in the mesh when you know for a fact that you did not have any holes. Now another thing that is a major issue is the mulit-textured objects thing. Now you can effectively import mult-textured things in to FPSC with out creating texture maps. Now the problem that this presents is the object has to be dynamic. You can edit the file preferences for each object but will never truly fix the problem unless you take the time and UVmap and add a Texture map to the model. the engine plays different roles when calculating static and dynamic objects.
I recommend you Create the UVmap and then add the texture map to the model. this should eleviate alot of the collision problems on the terrain. In fact I think I am going to do a quick test. I will post my findings here for you.
By all means do not get discouraged. just keep on keeping on1
Regards,
RF