Sorry for the late reply but somehow i missed this thread.
All i can add to the tutorial thread is that all you really need to make the landbridges work is to edit map_heights.tga and they are working only on half of the map - if you have 2 lands separated with 1 pic of water and there is no landbridges then you'll have to move it 1 pic up or down (or left/right if the sea area is vertical).
Don't forget to check if on map_ground_types.tga there isn't an unpassable area - like the mopuntains near Tingis. And don't forget to delete the map.rwm.
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