The contact area of the car's structure, should be the only measured area of the square in rule.
" shadow".
It was designed to keep the cage plates from stiffening the car.
What you do inside of the 144 in , is only regulated by the 15in max side rule.
If you have guys measuring and adding the sides of the hoop/ base plate/box, etc, contacting the car structure, than I really think the rule is misinterpreted.