description.txt

Enables worlds up to 16800 tiles wide and 4800 tiles tall to be loaded. (Double the width and height of a Large world)  

Note that with mods loaded, it may not be possible to load a world that large due to memory limits. I recommend a 16800x1200 or 16800x2400 world as worlds that are taller than Large worlds tend to be boring.

Generate a world to use with this mod using TerraCustom. TerraCustom will load tmodloader mods, so you don't have to worry about missing out on mod biomes. (http://forums.terraria.org/index.php?threads/terracustom-for-1-3.35346/)