@sinsitroy - The key point is that you must have the following items associated with the mesh before you can export:     Now, I used to enter those custom_properties manually, but thats a huge pain. So instead I follow these steps:   The eRelatively quick-and-dirty version is the following: Import your custom mesh (xps, nif, tmc, whatever) into blender. Fit the mesh to the body Remove old parent/skeleton/bones/vertex groups (make sure to keep an