Thank you all for your response. I do have a Weber chimney, pizza is what on the menu for my first use of the grill, mid 40's in Houston this weekend (finally), I will probably start with 2 layers of lit briquettes spread evenly all around charcoal grate (6" empty circle in the middle) for my first bake and work my way up.
I will be using my Mighty Pizza Stone, a pizza stone with an adjustable heat diffuser, (I launched on kickstarter last year), the adjustable diffuser allow me to control the stone temperature to balance pizza top and bottom cooking rate for even bake.
My goal is to get the temperature as high as possible at the grate level (above the stone) without any mod to my grill, the higher the temperature the faster the bake time I can get.
So at 500F by the grate level, my bake time should be 8 to 10 minutes, will see how it goes.