Note: This procedure involves changing a game file;
create a backup copy of the file before proceeding. Select a map
file in the "maps" folder in the game directory (for
example, "LowerParadise"). Copy the file to a different
directory. Rename the map and put "cus" before the name.
(for example, "cusLowerParadise"). Cut and paste the
file back into the "Maps" folder. Start the game, go
into the options, then select "Custom Maps". The map
you copied will appear. Highlight it, then select "Load".