Paul, once your pizza business takes off you'll be able to buy your car back if you. But you'll be so busy making pizzas you won't even have time to drive.
Bummer about the glass. Good advice, next time lead with the squirrel/nuts story. Also, consider cutting the glass in a straight line near the break and pushing it up against the wall for a nice custom piece. Chip the glass like the other sides and no one will know.
Back on the oven. I'd run a test with heavy duty aluminum foil under the stone and/or play with the upper venting. Heat flow is hard to predict. Also, I'd guess you will have better results with the lava rock near the stone rather than the base. At the base it does more choking of the airflow, at the top, perhaps a little better radiation on the cooking surface (but convection heat to the stone is far more important).
That 900F result in 20 minutes seems weird to me - too hot, too fast. Using an IR gun, I once got readings that didn't make sense and it turned out I didn't measure the stone temp. Even though the dot was pointed on the gun, the heat reading was off the cover - in my case.
Dave, good ideas for the table. I'll run it by the wife.
She wasn't too pissed at me, I was exaggerating a bit.
I don't remember the temps exactly but they were in the high 800's, but it was b/c of the thin stone and really no true heat barrier. I think for that one I also had the burner going at 3/4 power. BTW, that thin stone bit the dust with the glass table. It was sitting on the edge that ended up cracking.
I agree about the lava rocks needing to be higher up. Here's the latest mods. Tell me what you think and if it will work. Well I'll give it try and let you know if it works or not.
1st mod is I decided to put a metal disk to lower the dome a bit. This will help with airflow a bit more and decrease the amount of air circulating in the dome.
2nd mod is to create a heat diffuser/barrier right under the hearth. Instead of hanging a pie pan, I decided to use one of our old TFAL pans. Pie pans are around 9" and the pan is 10". It should work better since my stone is right at 12".