In another thread, I've talked about my miserable failure cooking a pizza in a grill over a campfire. One suggestion was that perhaps I need to erect a "roof" of quarry tiles above the pizza to apply heat from above. I'm certainly not doubting that. I just don't understand it.
In my oven at home, I cook the pizza on the bottom rack and there is a lot of open space (14") above it, but it cooks just fine. Why would having stone a few inches over it help?