A bit of a note, I am still having problems after following the modding advice I found in the tutorial.

In this explanation, it says that I simply needed to copy three files from settlement A (in this case, Northern European Wooden Castles) into settlement B (Northern European Castles).

Custom battles don't allow me to fight in castles. Whenever I put my cursor over "castle," it switches to "fortress," and then the word "castle" disappears from the custom battle menu.

When I besiege a Northern European stone castle in the campaign, on the battle map it shows up as a Middle Eastern castle with some Northern European buildings inside of it.

Help!