I'm curious, how did you modify the thermostat?
BenLee, the instructions are essentially (though not specifically spelled out step-by step) all over this this thread:http://www.pizzamaking.com/forum/index.php/topic,2334.0.html
From the factory the thermostat is maxed out around 550F or so, but by opening the unit up, and bending back the "limitor tab" on the thermstat, I have been able to get the stone up to over 1000F. But there are drawbacks--at these high temps the plastic housing of the unit gets up to almost 350F and you need to be careful around it.
I have also modified it by closing off the many oblong side vents that surround the unit on the lid where it meets the base. I also place a heavy brick on the lid while pies are baking (there is a gap between the lid and base that grows to 1/4" in the rear)--all of this in an effort to trap heat in the unit, and to raise the temperature in the baking chamber.
There has been other tweaking as well--I cover the toppings with a 9" round piece of double foil for the first 2 minutes of baking to allow the crust to brown but to try to deter the heat from melting the cheese too fast. There has been a lot of tweaking with the Pizza Bella actually, and it does not just produce pies like the one in this thread like--SNAP--that. There is much more coaxing and experiementation required. I do NOT mean to make anyone think this inexpensive unit is an easy answer to a great pie as is.
It's as I'm sure Marco, Pete, Bill SFNM, Villa Roma, and many others here will tell you, making great pizza is much about experimenting and learning, rather than hard and fast rules or recipes, or even ovens (even a Neapolitan made brick oven, as Marco will often tell us, needs a Master Pizzaiolo to coax a great pie out of it).