NetherYLevel - dniym/IllegalStack GitHub Wiki
CHILD OPTION OF Block Players Above Nether
Adjust the Y Level of the nether, useful for custom world generators. This option allows you to change the Y level that IllegalStack considers to be the Ceiling of the nether, you should never need to change this value unless you're using a custom world generator and the ceiling is at a non-vanilla height.
To adjust the Y level of the nether ceiling use the following command.: /istack value set NetherYLevel (0-255)
This protection has no extra options.