Max mini late 2012 running sequina but I also want to partition to run Windows 11

Hi I currently have Sequina running via OGLP and want to also create a partition to run Windows 11. Clearly can’t use Boot Assistant but lots of alternative routes available online.

The issue I have is that they all require a partition on the disk to install, but the instructions to partition the OGLP disk all fail for me for some reason (-8 error code).

I’m sure the disk isn’t corrupted and FirstAid on the disk confirms this. What am I missing? The drive was encrypted when Sequina installed after formatting.

Am I going mad ?