I have made some updates to the RGB texture loader of ModelConverterX. The first one is a bug fix for textures that are not square and the second one is added support for RLE compression in the RGB textures. With this the most commonly used RGB textures should be read by ModelConverterX.
For those not familiar with RGB textures, this is a texture format designed by SGI that is usually used for OpenFlight models. So with this expansion of the RGB texture loader it should be even easier to convert your OpenFlight models to FSX or Prepar3D. The mass texture editor can now take care of the texture conversion from RGB to DDS.