As in title, I was trying to mod the District leveling condition, and want to know if I can change the general level-up rule or the individual level-up rule of each district. 

I found something like NumberofExtensionAround in SimulationDescriptors[Class], which sounds like it is used to check how many other districts are around a district, which in turn is used to check leveling. But changing that value does to seem to make any impact on the district level. 

So how to I change the District level-up condition?