I did a test burn with a new burn channel top and chimney front, somewhat different configuration that crowded the barrel even more and made the system size even larger.. The fire was slow to get going and the system never got anywhere near as hot. Barrel top maxed at about 400˚F. On the plus side, the replacement pieces were unaffected.The bottom is still in one piece, but the sides have collapsed.
I suppose I will do some sort of clay surface stabilization experiment next. Don't get the wrong idea if you catch me digging in the kitty litter.