Yes, that guy has been quite cute in the way he's done the maths.
I saw it a while ago and copied his theory/approach into my app, not so much for the angle values but because it compensates if you don't have the strings parallel to the body.
As long as the strings are parallel to themselves you don't have to spend a lot of time getting them set up around the car. and in my case that always took longer than actually doing the measurements.
Brian