[Coco] Converting CoCo 3 to USB power

[Lee]

I watched this video (https://www.youtube.com/watch?v=tTwTgGR-jSU&t=867s)
on converting the CoCo 3 to USB-C PD power, and would really like to do
this.  However I have some questions.  He mentions the two of the 3-pin
connectors going to 12v and the 3rd pin going to ground, yet the Googling
I've done seems to indicate the original power supply output 5v and 8v
(NTSC model) to those two wires.  Am I missing something? Is it fine to
supply 12v (or even 9) to both?  USB-C PD can negotiate 5v, 9v, 12v, ...
from the power source.  Is it safe to provide the same voltage where the
CoCo is expecting +5v and +8v?

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Lee