Back up your original copy of rules in the Thrones and Patriots folder.
Then paste this one.
This "mod" basically just makes it easier to make larger scenarios which attempt to depict big areas, otherwise things tend to be too close and it loses some realism.
Hope you enjoy this, and as a side note, after saving a scenario made with this bigger map setting, it will work with the original copy of rules. So you don't need the mod to use a scenario created with this, you just need it to have the scenario creator make the maps bigger when making stuff.
(I'd suggest that you make one big blank map with this and save it, then reset the rules to the original file. Then you can just mess around with the new map and save it as a few different things so you can still take advantage of the mod)