Sadly, the CustomPlanets.xml file isn't compatible with designed maps... thus, why we can't have anything other than random surfaces for these!

One more thing SD should really consider fixing for both DA & TA in future updates.

That is exactly what is stopping me from creating maps, scenarios & campaigns for X-Worlds, btw.

Yes, Xrati... we certainly can swap whatever surface graphic files, but since the runtime distribution process picks these planets at random from what is already available in the folder and from pre-defined values found in PD or TCS xml patterns -- there's no other solution than some encoded & direct full compatibility with CP file listings (modded or otherwise).