After I spent the time under the lift, I realized I was missing some measurements. After some googling, I stumbled across the body shop manual... which meant the whole tape measuring exercise was unneeded. Still glad I got under the car, though, and the pictures help me put things into context.
Body Shop Manual
![Body Shop Manual](https://kraln.com:443/rx8/content/images/20231001122016-straight%20line%20dimensions.png)