The Heightmap Surface plugin that Micheus worked on a long time ago may help you with terrains. You would have to use an older version of Wings since the plugin is not compatible with Wings v2.* versions. You can have old and new versions of Wings installed at the same time.
Here is a link to info on the plugin.
Heightmap Surface plugin
oort
Here is a link to info on the plugin.
Heightmap Surface plugin
oort