Alright, today I reached out for help mounting my brushless motor so I posed the question
here and received help from a fellow forum member. AAmed with a better understanding of what is what with regards to the firewall markings, I set out to mount the motor, and I did just that.
The first thing I did was to dry fit the stand off's
Then I made a paper template of the cross hair markings on the firewall, making sure the cross line was the same on my paper as on the firewall.
You see that cross hair on the firewall represents dead center of the motor shaft. This offset is to compensate for the thrust angle built into the firewall, yet to ensure the motor shaft is all lined up when it exits the cowl. It's pretty ingenious. Anyways I measured the center of the stand offs and laid them out on my paper template.
After I marked and drilled the stand off holes, everything fit perfectly. The spinner is dead center of the cowl, and the spinner gap is minimal.
All I have left is to button up the wiring, and build a rear battery tray to better center the weight on the two 6S packs that make up my 12S system.