I flattened the curved steel that made up the top of the tank that was cut off. Well got it close to flat at least. I used that to fully plate the area under the steam plans which leaves about a 1-2" air gap under the pans after the insulation was put in.

The fire box is fully lined with insulation and I put 1" thick firebrick over the insulation at the bottom of the firebox. The brick goes up about halfway up the side of the fire box. The brick is just there to protect the insulation.

I made a fire grate out of angle iron and it sits about 6" off the very bottom of the tank to make room for the AUF.