DIY Alignment: Am I doing it right?

[TheBandit]

For my car, I can easily check camber by placing my angle cube on the end of the hub. From my research I understand caster can also be measured this way, but requires a bit more work to sweep the tires through a suitable steering angle. After looking at different tools and methods, I came up with a method and explain it in the following YouTube video. I'd love to get feedback on whether this method is correct and if there's anything I might need to do differently.






In summary:
- Start with suspension settled and car steering ahead
- Drive onto folded-over trashbags to use as slip plates
- Place tape on the ground parallel to the wheels to denote zero steering angle
- Place tape on he ground 20degrees in either direction from zero steering angle using a protractor
- Turn wheel 20 degrees one direction, measure camber, then repeat in other direction
- Take the difference in camber measurements and multiply by 1.5 to get caster
- Subtract driveway/garage floor slope (assumes car is level left to right, but driveway slopes down toward rear of car)

I got the multiplication factor for the +/-20deg steering sweep based on the instructions for the Watkins Smart Camber tool which can be found here:
https://static1.squarespace.com/stat...14+7-20-19.pdf