I'm not angry or saying its the fault of the author for this bug but I spent 3 days (Or arguably more) building a nether fortress farm to farm wither skeleton skulls. Using other mods the bounding box was visible but it extends all the way to the bedrock roof.

The issue with this mod is that it makes farms pretty much impossible to build by just using the bounding box and nether bricks. Which is a huge killer for this mods usability for a regular play-through.

Solution: Greatly decrease the size of the outside bounding box of the fortress, and make sure mobs can actually spawn inside this bounding box. As seen in another bug post, it doesn't seem like the outer bounding box dictates whether or not mobs can spawn.

Unfortunate :/ .