The maximum pizza size my pizza stone can accommodate is 14 inches, which is why I downsized the Raquel recipe to that size. My usual practice is to bake on the stone (on the lowest oven rack) for about 5-6 minutes and then transfer the pizza to the uppermost rack, just below the broiler, and bake for about another minute or two under the broiler. Sometimes I will put a second stone on the top oven rack and preheat it, along with the lower pizza stone. Whether I use the second stone or not, I can't say that I notice a big difference. I usually turn the broiler on about 3 minutes or so into the bake process. Whether I use one stone or two, I preheat the oven for about an hour (a bit longer if I use two stones) at about 500-550 degrees F.
I agree that it may make sense to try a 500 degree F bake temperature (Tom Lehmann advocates around 450-500 degrees F) and lengthen the bake time, if for no reason other than to see if that improves the color in the crust. It may well have been that opening the door a few times lowered the ambient temperature of the oven by enough (I bet it was quite a bit over a hundred degrees) to prevent the top crust of the pizza from browning up sufficiently, even though the stone was still very hot. Opening the door to move the pizza from the stone to a position just under the broiler is not a problem because of the high direct broiler heat. In fact, the oven manufacturers often suggest that the oven door be kept ajar during the broil cycle.
Please let us know the results of your next attempt.