The latest ModelConverterX development release contains a new feature that you can also do a reverse earth curve correction. In the previous versions you could already correct your model for the FSX curved earth, but with this new feature you can also undo such a correction again.
Besides that the Coordinate Converter tool can now calculate either latitude, longitude or flat earth XYZ or geocentric XYZ from any of the different formats. So this will be useful if you need to convert between them while developing.
The video tutorial below explains these new features as well.