Yes, chunking seems to be important for mesh terrains. Damn, I knew Josh would delete my posts, because he thinks it's "derailing". I was aware of that, and tried to make an Article (=User Tutorial) about mesh terrains, but the damn IPboard software is always buggy somewhere. I noticed that with a single terrain mesh, the 4096 res is still not high enough, so one should use smaller terrain chunks, and maybe one global flat ground to guide the composition.
EDIT: Hmm, I think IPBoard had some rollback, because also status messages were deleted.