iATKOS | United Kingdom

Before you begin to play with OCLP, use either Carbon Copy Cloner (CCC) or SuperDuper! to make a bootable version of an APFS formatted copy.

I use SuperDuper most often and format it as APFS; then clone my existing system so that it is bootable. Test it first. I have had to resort to using this a handful of times.

Having a non-OCLP backup will save you headaches if you screw something up.

Also, once you convert to OCLP, SuperDuper! does not allow you to create a bootable clone after. So back up your User files.

What as worked in the past after experimenting on a Mac Pro 6,1 is that I roll back the root patches, run SuperDuper! and then reinstall the root patches. This creates a copy, but it is not bootable.