Thanks for the kind words guys. Tampa, I really appreciate your input. I'm especially interested in your initial result that 700F was a hard target to meet. When I read that and saw the pictures, I figured you were limited by the lack of venting out the top and that problem would be corrected when you cut the side slit. But I think you said the temp increase was due to removing the diffuser stones - in either case, it seems the flame was not getting to the stone, or you would have seen a big temperature jump. If you choke the airflow, because of stones, or because of narrow gap between the pizza stone and sidewall, or because of the outlet, etc., the hot air will get backed up and tend to flow out the bottom.
Yes you are right. My initial issue of getting temps above 700 had to do with 2 factors. Using the lava rocks at the bottom as a diffuser barrier and setting a 13" pizza stone on top of firebricks. The 13" stone left on a 1/2 gap around the perimeter. That along with the unmodified vent lead to the lower temps.
I have since remedied both factors. I have increase the perimeter gap to 1" and have modified the lid vent.
After having burnt a few pizzas on the mbe, I'm convinced that 650-700F temps is where I want to stay for now. Any hotter and the bottom burns too quickly. Even if I can equalize the temps from above and below or in a perfect world get higher dome temps, I still have to rotate the pizza since the edge near the vent won't brown. That means the pie has to sit in the oven longer. OK by me since I like a crispy bottom and rim anyways.
On my 2nd bake, I removed the lava rocks and used a smaller 12" stone. I place the stone on a 12" metal disk and had a layer of tiny pebbles underneath to disperse the heat so as the think cheap stone would crack. This is when I got 900F temps in 20 min. Way too hot!
So now I have my firebrick hearth cut and in place and a new lid vent, but the hearth is still too hot compare the to the air circulating above the pie. To remedy this, I went ahead and added an 8" disk to the the dome to lower the ceiling. I hope this helps concentrate the flow of hot air a bit better rather than trapping some of it in the dome. The dome of the smokey joe is pretty shallow to begin with.
Next step is to add back the lava rocks or add a diffuser layer. But where to add that layer? Down low at the bottom grate with lava rocks or just below the hearth by hanging a ceramic plate? Well Villa Roma added hung a ceramic plate just below the hearth and I can just about see his reasoning.
Reply #703 http://www.pizzamaking.com/forum/index.php/topic,4753.700.html
The potential issue with having the diffuser plate (with lava rocks) down below, is that the heat can encompass the lava rocks and then rise straight up into the middle of the hearth. The potential advantage of hanging a diffuser layer below the hearth is that it will absorb most of the heat and hopefully distribute it to the perimeter. I'm not sure that this is how it will work out but that' how I imagine it anyway.
Anyways, I don't have a 8-10 ceramic plate so tomorrow I'll go to the thrift store and look for a cheap pan. I plan to take the handle off and fill it with either ceramic briquets or pebble rocks. Anyways I'll keep you guys posted on my progress.