I just got a hearthkit, and was very pleased with its inaugural run with a couple pizzas and loaves of pain au levain (margherita was beautifully cooked in about six minutes).  However,  it took much longer than expected to preheat all that mass because the oven kept cycling.  The hearthkit's thermometer got up to the mid 300's relatively quickly, but at that point my oven thermostat, set at 500, started to cycle.  It was well over an hour and a half before it was usable and I never did get it quite as hot as desired.  I'm wondering if anyone has tried to trick their thermostat into leaving the element on continuously until the stone is ready?  Or, can someone recommend a different solution?

thanks a lot, Logan