User blog comment:PsiCubed2/Question: General breakdown of levels up to Second Order Arithmetic/@comment-30118230-20180204192313/@comment-30754445-20180205110703

Ah. So even  Δ12-CA+BI isn't enough to get us very far.

This is getting really interesting. I hope you don't mind if I ask a few more questions:

1. What about Δ12-TR0 and Δ12-TR? How strong are these?

2. Can you give me an example of a subsystem of Z2 that has a PTO comparable to ψ(εK+1)?

3. Is there a place were I can find a more comprehensive list of subsystems of Z2 up to Π12-CA0, ordered by strength, including systems we don't yet know how to fully analyze?