Do I need to insulate my flue? and other parts

[odsch]

I made a galvanized steel on top of the brick arch flue. My IR thermometer reads it as 60-70c when the oven is firing. Will it eat away heat from the dome? Do I need to insulate the brick part or even the GA flue? Like in the pompeii oven plans
Also I guess my perlicrete insulation is not that thick yet as it is 40c to the touch, Do I just slather a new coat of perlicrete?