click to embiggen
Above is a recent iteration of my Dark Country map. The green hexes represent the area cultivated by the nearby settlements. Each hex is 6 miles across (to match the B/X movement rates). I decided on the amount of farmland in a completely arbitrary manner, but it largely came from the fact that my earlier attempts (using 10 mile hexes) were a bit too big. Here the farming production has doubled but the size of a hex is smaller. I also spitballed a bit based on Rob Conley's figures.
Still, I'm very unsure about the level of settlement in the Dark Country. It's supposed to be a Pagan Wilderness, and it relies primarily on trade and forest products rather than agriculture (the large amount of precipitation makes it poor farming land), but compared to Blackmoor or the Wilderlands settlements are sparse. Granted one can assume that hamlets and thorps dot the little green hexes, but for the most part theres only a small concentration of "cities" (they'd be towns in any other D&D setting) and walled villages. Right now -- unless I miscounted -- there are only 17 villages and towns on this whole map. Is that too low?