Craig, since you are using low conductivity biscotti for the floor, don't you think the balance can be made using higher conductivity firebrick and the pizza being closer to the radiant heat? I think a 36" is as small as I would go if you plan on using it fairly often at any rate.
I'd have to say no. The floor conductivity has to balance against everything else going on in the oven. The higher the floor conductivity, the faster the bottom is going to bake, AOTBE. If you increase the IR (and convection) to balance the floor conductivity, you are also going to increase the floor heat, and it will become a vicious circle. The only way out will be to dome the pie before its ready to be domed. The conductivity of the floor has to balance IR that is in equilibrium with the floor.
Likewise, I don’t think it is a good solution to balance higher floor conductivity by increasing IR on part of the pie by moving it pie closer to the fire or closing the distance between the fire and the wall. IR varies as a function of temperature^4, so as you favor the fire relative to the far wall, your heat imbalance increases exponentially – and not by a little exponent, but a big one.
I’m going to go with the Neapolitans and say that 100cm/39” is really the absolute minimum required to get a reasonably balanced heat. No science behind that – though I could put some numbers to it if someone wanted to discuss it in more detail – rather it’s just from experience with my oven.