Shaun, I'm gonna save you some time and a few burnt pies and share with you what I've learned.
We get top heat by directing the bottom heat up instead of providing the top heat from above like in the ideal situation of a WFO. The ideal scenario is actually the opposite of what we have. A higher top heat compared to the bottom. The best we can do in the LBE is to equalize the top and bottom heat by using heat barriers and low heat conducting stones like firebrick or quarry tile, or scored FB/QT as VR has done.
Many of us pizzageeks are hooked when we see pictures of charred rims, leopard patterns, etc much like what happens to men when we see b@@bs. We tend to get the deer in the headlights syndrome.
In our minds we equate charring with high heat and so down the wrong path we go. The problem with high heat, and short bakes is that they can give you that nice looking rim but it will often soften up shortly after the bake. To get a nice crisp rim in the LBE, we have to actually do the opposite from what we think is right. Lower or keep with a temp of 625-650F and bake it for 4-5min as Scott says. It'll be around 4 ish min, and you'll get that nice crisp charred rim. You may have to tweak the hydration ratio a bit.
It's all balance. You can cook a pie at 700 for 3-4m and get a crisp rim but you would have to go with a moderate to low hydration dough. You may like that I don't know. Either that or use a less conductive stone. What works for me is a high hydration, 650F, 4+ min bake on FB or QT.
The 2nd issue with burning in the LBE is HG flours. They can tolerate up to about 725F. Higher than that and you are looking at a burnt bottom. And that's if you have your heat equalized already.
3rd cause of burning is overfermentation. The more the dough is overfermented the more residual sugar is available to burn. Scott, Peter, and I discussed this in my MBE thread somewhere. Overfermentation coupled with high heat of 725F+ and you're toast.
4th issue is sugar in the recipe. For the LBE type cookers, I would avoid sugar in the formulation. Hope that helps.