I am trying to use this mod along with the Infinity Cave mod, but when i do, the world always cuts off at y=-64 instead of continuing to y=-128.

I am not sure if this would be an easy or hard fix in this mod, but it could be nice to have compatibility with mods that add extra depth to the world.

this is the mod in question:
https://modrinth.com/datapack/infinity-cave

The Fabric version of Infinity Cave appears to have some code to provide special compatibility with Tectonic. If you're using the datapack or Forge version, you're out of luck. If you're on the Fabric version, this issue should be brought to the Infinity Cave dev.