Nice experiment, KKash. My guess is the stone directly below the steel leached heat from it, or prevented it from reaching as high of a temp as you wanted on the steel. When I cooked my pizzas (granted, I've had limited time to experiment thus far), I had foil/drip pan on the rack below the steel, and heat-soaked the steel directly on the grate for a good hour before starting my first pizza. The crust was awesome. I'd also guess, from other comments I've read from Dennis and others, that you're just burning unnecessary charcoal to heat up the stone if you're not using it in there.