Scott, thank you for your feedback. I can't even begin to say how much it's help me progress.
With my current set up the heat in my mbe oven is not yet ideal. I want a top heat that is at least 50F hotter than the bottom. I want the top to cook a bit faster than the bottom. As it is the bottom outcooking the top by a small margin. That's the reason why I was searching for a lower conductive hearth. Another possibility for this slight unevenness is the air gap between the current stone and the sloping lid. It is < 3/4" and even less if I place a pie near the edge. As the crust rises (into the dome) it starts to restrict some of that air flow. Or at least I think that is a potential problem. No biggie, as air will find the path of less resistance and flow around in the other areas of the perimeter.
B/c of this slight uneven top and bottom heat in my current setup, I have to actually bake around 3 mins to get a good charring to the rim. If I lower the hearth a bit, it should increase the airflow to the dome and possibly get me decent charring in the 2 min realm. IF i can do this, then I can make a thinner pie, have it bake faster than 3min, and get a great texture. As it is with the thick firebrick hearth, the bakes have to be longer and that equates to a drier pie if it's thinner.
I'm glad you mention my pies are getting more varied, as I was thinking the same. That caputo pie looks very different from my previous caputo pies. It's likely the fermentation regimen and heat differences. I'll have to do an experiment on that down the road sometime.
I just heard back from the fibrament folks and they can't custom cut a round 12" stone for me. I had forgotten about how brittle it is so thank you for reminding me. BTW, is quarry tile a lot less brittle than fibrament? Can it withstand thermal shock comparable to firebrick?
If I have time today, I'll start making the cuts to the quarry tile and see if my theory about airflow is correct. It is dense quarry tile, so I hope it won't be too hard to cut. Even if I end up with the same conductivity as the firebrick, I may be able to benefit from it's reduce thickness. I'll experiment with just one layer first about 1/2" and then double it if I need to. I'm also considering cutting up a thin steel pizza pan and placing that under the single layer of quarry tiles.
Have you tried the no buffer, low pre-heat approach yet? Heat the stone to 600, crank the heat and put the pizza in.
I have but didn't get good results. I tried the no buffer, load it at low temps and crank up the juice approach and got burnt pies earlier than expected. It could have been due to some overfermentation, restricted top air flow, bad karma, or some other unknown reason. I plan on revisiting the technique once I get my dough fermentation times down to insure it's not a fermentation issue but rather an oven setup issue.