Are you talking about resample files? I'm that case drawcalls don't really apply, that's for 3d objects.
For resample files it's still a good idea to make them as big as possible. It's more efficient to have to read less files. The bgl file formats is quite optimized, so that the engine...
Do you mean the mesh of a 3d object? Mesh is often used as term for elevation data as well, but I don't think you mean that.
I don't think combining mesh for objects helps a lot, as xtomdl already optimized on export.
It's weird that the preview is empty after you load the object in the wizard. Can you try to disable the option to filter out non-ground polygons or to project them on the ground? I guess one of those might be related to nothing showing in the preview.
I have just changed the code of scenProc to be more robust when the library that reads the spb file throws an error. So it will not crash anymore and should continue. But for the spb file that could not be read no GUIDs are extracted of course.
I'll see if I can install the latest P3D here...
So it seems there is some error while reading the spb files. I should make scenproc more robust for this,so that it doesn't crash.
But maybe one of your spb files is corrupt? It's the first time I hear this issue.