[Fat Charlie]

Perfect is the enemy of good enough.

With all the variables involved there isn't actually a perfect. Strive for it all you want, You can either come up with the ideal perfect, which ignores all vehicles already produced, or a very specific perfect for one particular vehicle. On the other hand, you can use a rule of thumb that tends to work in more circumstances than not and on more platforms than not.

The rule may be outdated and fall short of modern ideals, and actually fail on many vehicles in many circumstances, but then so do the cars we drive. If it helps more than it hurts, it's a good thing no matter how many instances you can point to where it falls short of ideal.