NOTICE: In BSC 1.6 .plist file modification is obsolete; your .sqlite in Documents>db must be edited in conjunction with any .plist file for changes to occur.
You've likely explored the 3 different multiplayer maps( Islands, Sea, and Random Islands ) to their full extents. However, Drill battles only use the Sea map. Editing the code will allow you not to switch maps, but at least to spawn in individual islands with locations of your choice.
You can enter an island ID under the 'enemies' array in mission.plist ,this is extremly similar to the process described at the Multi-Ship Naval Battles page. If you are unexperienced it will be best to read through that page first.
Possible island IDs are:
Here is a sample of code:
Note the z-coordinate. This can be used to adjust the height of the island above the water. While not necessary, some islands are inconveniently tall. Also make certain neither your ship(s) nor the enemies' ship(s) are spawned inside the island. Islands differ in size, but some are extremely wide.
While this is under the 'enemies' array, a 'quaternion' value and a 'strategy' value are not necessary. Unfortunately, the island will be displayed as an enemy on your radar and will have a health bar hanging above it. While slightly annoying, it will at least give you a distance reading in kilometers.
Finally, make sure that your 'goalValue' integer does not include any islands, only ships, as islands cannot be sunk even when classified as an enemy.