So I just spent a couple of hours trying to create a custom race.
I read the woeful modding guide , read a few previous posts, had a look in the Mods databank and then attempted to create a new race.
What a waste of time. There is clearly a heap of stuff hard coded in the software and it is not really modable. The XML file tags are not documented. The XML content is ignored for additional races and for modification to existing races. There are no errors flagged for bad content, there are no working examples, etc..
I challenge anyone to point to a race mod that works (and I don't mean just swapping a image file).
Now this is all fair enough, but Stardock have advertised how modable it is. (I mean they have a section in this forum for it).
But if it doesn't work, they shouldn't push the modding feature.