hey ravage,
your theory sounds correct, but did not work out for me.
It might work with slicks on the car.
With street tires, there is a lot of the "patch" area that is not actually rubber touching the ground.
There is a lot of void in the tread recesses and that messes up the calculations.
If you had slicks on, then all the patch area would be tread and I think it would work.
But with street tires, the patch measures much larger than it actually is.
My 74 cuda with 440 calculated out to be 5259 lbs and showed that the rear is 300 lbs heavier than front which we all know is not correct.
