I am also trying to figure this out. I pulled the info from the xml file off the prefab editor after copying it to my prefab folder. And in my nitrogen folder i edited the prefablist.txt file with the following line under custom pois: Mall_DOD,COMMERCIAL;RESIDENTIALNEW;RESIDENTIALOLD;RESIDENTIAL,1,-1,137,66,118,industrial;downtown.
I have created about 6 maps now at 8k size and used the world editor to move around. I have yet to see one get generated. I have seen multiple Izea's and spiral library's which i modeled the settings after.