Update on my Matrix installation:
It looks like the Matrix is successfully installed because I can get the EvolutionX dashboard to come and I have test-run many game backups. I am running Evox D.6 Eject Fix BIOS and EvolutionX v1.8.3752.
However, I still havel the frag problem. The machine turns on, then off, then on, then off, then on and blinks red and green.
I found a way to force it to start even though it is fragging:
After you power the XBOX on, it goes on temporarily, and then turns off twice. Just as the green light goes on, press the DVD eject button. That sometimes starts the unit on the first power up attempt. If you fail, turn off machine, then turn it on and try the DVD eject trick again. It almost always starts up on the second power on attempt, usually by the second time the green light goes on.
With this approach I have been able to get the XBOX to start up everytime (although I have had to do 1 or 2 power cycles).
Ultimately, I am just going to solder the D0 point. However, I am keeping it with a pogo pin for now just in case I blow the unit and want it replaced.
Hope this helps someone.