why would I want/need to do this?
*> If you load a new set of terrain textures for which a fartiles isn't supplied
*> If you load a new set of textures for which a fartiles download is optional, and you wish to avoid a ~25MB additional download due to bitrate limitations
*> if you load a new terrain (as opposed to textureset) update, and you want to avoid seeing a discontinuity in the terrain at mid-distance before a new fartiles is offered for the particular textureset you are using, or if no one posts a fartiles update for that particular textureset.
*> if you construct your own textureset by mix-n-match from all the textures provided in the many texturesets currently offered (each landscape texture is independent of the others, though the result may look a little inconsistent), so you need a custom fartiles to match your custom textureset.