Fixing the OPCODE support worked.  Thanks Nate.

 

Where can I find the file that was used to build terrain.gzb (I guess it is terrain.png) so I can get a feel for how it works?

 

Also, I can only build 2.5D terrain (no tunnels) as per the documentation, but could I offset two models (stack them) to achieve a two story terrain model?

 

Matt