Yes - or at least 1/16" When I used to have weigh in my car (200 lb. or so) I used a rectangular plate that was about 8" x 3", with the two mounting holes about 5" apart (the weights were made about 10" x 6" and came from a stock car shop and were pre-drilled). Underneath the floor I used large and strong fender washers.
You don't want that s&*t coming loose when you roll the car!
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