I have updated the preview in ModelConverterX. It now uses more of the FSX material settings while rendering. More concrete this means that the framebuffer blend and alpha test function options in the material are now displayed in the preview correctly. So you should get a better idea of how your model will look in FSX. I have not tested all combinations, but it should be how FSX will also display them. Some settings really give funny results, I am not sure if there is a useful way to use them yet.