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Legacy:Map Filesize
From Unreal Wiki, The Unreal Engine Documentation Site
The average filesize of maps has rocketed since the release of UT2003.
Some tips for reducing the size of your map:
- set all unseen BSP surfaces to unlit (those completely behind static meshes or terrain)
- set bsp surfaces where shadow detail is not needed to 256
- rebuilding lighting with DXT1 compression
- compress all (custom) textures that don't need an alpha channel to DXT1