I currently use fire bricks on a charcoal/wood fired grill and am getting a nice char to my crust, but it's not cooking at the same rate on the top. I was going to weld some kind of frame up to place bricks above the pizza as well, hopefully getting some radiant heat on top. My question is...what would be an ideal height to make this frame? How far up from the pizza should the second layer of bricks be? Thanks.