Cheerie,
I have gone through this exercise, and in my hands it does not work.
You get a lot of heat from the bottom through the stone, but very
little from the top, so things do not cook evenly.
Pizza on the grill, though is definitely possible, and easy, but
without a stone. I got the method from here:
http://www.thefreshloaf.com/modules/news/article.php?storyid=49
Works well for me, but the timing is such that I have to do one at a
time. I get too far behind if I try to make two together, since
things move fast.
Ian