Norma and friends, the method tom lehmann is using is to actually top the pizza, then cook it on the grill as if it were a normal pizza. I am sure it makes a good pizza, although I worry about a serious gum layer. Having never tried that method I am not sure, but the methods I am talking about are what is done at Al Forno in providence RI, which is where the grilled pizza was first introduced (to the US in a restaurant at least), and where it has definitely been perfected. I put it right up there with my top 10 favorite pizzerias in the US, and it is something I wish everyone could try.
Hotsawce The grill is as hot as they can get it. I am no expert, but it seems that after trying both that lump hardwood charcoal seems to burn a little cooler than normal kingsford type charcoal. Because of this it is really important to keep the coals burning red hot. If they turn too grey the heat seems to go down on my grill.
I am sure you can use any size dough ball you want to. I make large pizzas because my grill is over sized. Just be careful that its not too too thin, or it gets too crackery (for my tastes).
When I mentioned par cooking, I was referring to things such as sausage, onions, or any of the toppings that go on the pizza. The method I use for the dough is what is used at al forno, and there the pizza dough is put on the grill for a minute, flipped, toppings are very quickly applied, and the pizza is pulled off after a short stay on the grill. It also works to use a lower temperature, but as most of us have learned, a faster pizza can yield a different crust texture which is preferred by some. If you want a crispier pizza it is possible to do a slower bake and that works great too.
Good luck everyone!