I've tried 'appending' a custom solar system, but I can't get it to work. I've run into the same issue outlined in this post, under number 3.
Any guidance would be greatly appreciated.
In short the only way I was able to make it work, was to copy the StarSystemDefs.xml to my mod directory, and then to just add my custom solar system. (Overwriting the default), which really wasn't what I was shooting for.
Thanks in advance.