Can't say I've tried pre-heating the cast iron pan on the stove top before with oven, but did want to warn you about putting the cast iron pre-heated on the bottom oven.
I used a baking steel on the bottom shelf near the bottom heating coils and promptly burned the bottoms of my pie before the tops even had a chance to get slightly tan.
What kind of pie are you trying to simulate? NY? Neapolitan?
I've tried both, my latest try was a Neapolitan style. The NY style had some sugar, but the Neo I think had no sugar whatsoever. Perhaps that is what is making browning so difficult.
The Neo had Buffalo Mozzarella that came packaged in a water tub. I had a feeling cheese that wasn't low moisture would be a problem, but I had no idea how much. The pizza was very soupy on top; it didn't look good, but it TASTED great.
. The rim had good color, and the cheese melted perfectly on top. I checked the bottom a couple of times troughout the bake, and was surprised. I thought the pre-heating and cast iron would roast that bottom, but it didn't. It cooked, but it didn't put the serious heat i thought it would. It was this fear of overcooking the bottom that made me decide to place on the middle rack. If you're saying the bottom is too strong, but my observation is that the middle is too weak for the bottom, then I'll consider experimenting with a stove top start, or start with bottom rack and move to middle rack.