You need to flip the image VERTICALLY. Not horizontally. Which is what it looks like you have done. This only applies to the DDS formatted textures and not BMP ones.

So create your livery in BMP so everything looks normal when you are creating it. Then use a program like DXTBmp.exe to flip the Image and Alpha (if it has an Alpha), then save as a DDS DXT3 or DDS DXT5. That should sort it out.

Mark