1) Added the option to adjust the height of the nether ceiling checks. If you're using a custom world generator plugin this will allow you to tell IllegalStack what the custom height of your nether ceiling is so that BlockPlayersAboveNether will work with a custom nether.

This option defaults to 128, any players at or above that level will either be prevented from teleporting or teleported back down if they move above this level.

config:
Settings.NetherYLevel: 128

in game:
/istack value set NetherYLevel 128