Hi，Mathew, I got a chance talking with SAGE's sales person here in China, she said the thermostat controlled the upper and bottom heating elements, and the other thermostat send the message back to the thermo-meter which measures the temperature of the upper level of the chamber. not sure if this answers your question.
Since I am based in Shanghai, while this vendor located in Gangzhou which is more than 1,000 KM away from, and unfortunately they don't have office what's so ever in my area. it seems difficult to take a picture.
now they developed a couple of new deck oven, which has inside dimension of 1286*665*180mm, and 965*665*180mm, double layer. I am talking to them if they could modify the upper thermo control at 500 C, they will give me a reply tomorrow as she promised.
Do you think if this oven is qualified for commercial operation after modification in order to produce Neapolitan pizza proxy based on your experience using their oven?
That would be great;thank you. If you could take a picture it would be greatly appreciated.