We built this oven some months ago. We opted for a low mass solution since we don't want to wait forever for it to heat up. Also we wanted to be able to move it around, using 2 wheelbarrow wheels. The design uses 1 oil barrel cut in half, allowing for insulation between the two halves. Check it out at: youtu.be/1ahly6FVbyQ and leave some comments on Youtube if you like it or if you want to learn more.