Is there a way to blacklist overmap specials?

[Belcanzor]

Farms spawn its mentioned often. You can manipulate map generator, like distance between city, and farm dont appear or just few.
I know this is not the answer you seek but perhaps help.

No cities bigger than 3 streets generating

Made a new world, tried setting it for bigger cities but further away from each other than vanilla. Result: so far have found only 3 “cities”(and there are 3 more somewhere else judging by overmap screen). One of those is 3x2 streets, another is 4 houses, and the last is called a city but really is just a crossroads without any houses. The world was generated on one of latest experimentals about a week ago. Bug or some intricacy of mapgen options I’m not aware of? [mapgen]

Maybe this post help