~One man’s opinion~
7.5" Pad size, 6" backing pad + 1/4" all round clearance. The oversized foam pad isolates the backing plate from contact with the car's surface, so you can work without fear of damaging the finish with an exposed baking plate (as you can tell from my signature I need all the help I can get)
Experience unshared; is knowledge wasted…/
justadumbarchitect