Are you using Kanthal A1 wire for your heaters?

Such an oven is on my todo list, for both Aluminium and steel. To ease the switching burden and maintain a more constant temperature I plan to split the heater into two parts. One part will not be controlled but its current, to maintain a near constant temp a bit below that needed for Aluminium, will be determined by experiment. Then the controlled part of the heating elements will only act as a top up. Time will tell how well that will work.

I was surprised that you were able to get away with such a low power input, that is very encouraging because I only have a 5 kW mains supply and I was a bit concerned that it would not be adequate while lunch was being cooked at the same time. Aluminium requires very long soak times.