See here: https://i.imgur.com/EJU6Usd.png
It's technically using the full screen with the inventory at the bottom and fps counter at the top. Surely this is a simple setting somewhere I'm missing? Any ideas would be greatly appreciated.
Usiing Forge and Chroma Hills 1.12.2. 1920x1080 if it matters.
It does not do this when loading up plain 1.12.2 vanilla.
After further researching, it actually looks like the black bars actually cut off what should be seen. It is not a compressed view. The arm is actually cut off and shorter than normal. Doesn't make since why it'd do this or this would be an option.