I do think there may be merit to red kiosk's "scooped up" argument suggesting that more heat flows as the stone height increases.
With all do respect to Red, I just don't think I can get behind that argument.
This oven is built too "loose" and with much varying degrees of tolerances. Lets take a look at my first pic. With Reds glow bar removed it is easier to see just how much this thing leaks and that leakage continues all the way around the perimeter of the heat shield. Now, with so many channels for the rising heat to travel I don't see; even with burner directly under turntable, the potential for this platter to perform a "squeeze" effect of the flame against the opposing heat shield, thereby increasing velocity of flame and subsequent upper chamber heat increase.
Looking at pic #2(thank you communist,and wish you would post your tech here cause good stuff gets lost over there) doesn't it become obvious, eazzy peasy if you will, that this is all just a matter of burner psi and deflection off of upper stone. I almost fear to think of what a beast this grill would be if a small strip of material was fitted and seam welded, to close the gap, between the bottom leading edge of the heat shield and the exterior panel. Momma Mia!
Anyway that's jus my $.02 worth....or should I say; "The Theory of Bob" !