may be you should post it on z9 general topics https://bitcointalk.org/index.php?topic=3509006.1480 not on this pool/fork topics.

IMO ...also not an expert
considering
- current thermodynamics law
- chipe temp measurement is not 100% accurate (may be close)
- i do not know the placement of measurement sensor
- other things
you might want to (DWYOR)
overclock it more... I believe the stable oc is now at 15-17...you might get 20 (or burn it before you get to 20) ...by deceive the temp sensor
but again.. I just tempting your couriosity, and other who has spare/experimental unit at home... in case you do..post it ..will you ..on generic z9 mini talk  
I ve read somewhere in the forum ..he/she has fried his/hers z9 ..most likely by OC it (sorry forgot the detail)
The point is ..consider the risk..

nevertheless its very interesting discovery