I was testing without the fan, sort of a worst case "can this catch the house on fire" test. That was when I decided the heat sink was not making good enough contact with the cartridge heater and I need more flexible wire to tie it tightly. I have an unused aluminum heatsink from a flourescent ballast, maybe I will try that, those ballast can get extremely hot also.
Front view, door open, before fan and heater were added
You have put alot of work into this I can see. Looks Good!! Are you going to hatch in this? I personally do not use the metal "boxes" in each rack for several reasons.