Plus the weight is on the suspension which makes it worst place for it. Not even accounting for unsprung weight of the rotor.
I had upgraded stock brakes in my red z and did a few solo II events and lots of heavy driving and never had a problem with them. I know if I had to do a road course I would have had to upgrade them. I was running hawk pads in front, new rotors, metal brake lines, Green shoes, and a 15/16" master cylinder, oh and motul 600 brake fluid.