So, going to buy the new diffuser plate soon. It's a nice add. So much easier to clean for many short cooks. The 640 should be able to make a directed high heat oven for pizza at 700f+ using heat bricks and a heat plate etc.
By placing the bricks to allow the direct heat from the flame to enter a heat chamber you might be able to create a oven where Mariana pizzas and other fast cook thin pizzas could be made.
Any thoughts?