Alright -- I've successfully overclocked the Z9 and I can now build flashable images so the modifications persist across reboot. I'll post a new thread in Altcoins later today with a link to the 575Mhz image that others can test with.
Thank you for keeping us posted as well as for documenting your process! I hope you'll add a link here to your Altcoins post when it goes up, very curious to try this out!