I am having the same simobject issue that others have had. Trying to add a Cessna 208 repaint livery package to my existing mission package using the Project Editor. I understand that the original aircraft needs to be part of the package to generate the repaint properly. Still, the SDK example is vague on how to add the existing model (in this case, the 208) as a separate package under the project so the livery will adequately generate.