21", cordierite stone, 600°F. I start the fire, get it to ballpark temperature, which takes an about an hour, add more fuel, the grates, steel, and stone, then let it heat soak another hour or so. The steel and stone are on the upper (as opposed to main) grate with the short handles down, so the stone is slightly above the lip of the KK. I find I can hold the temperature longer with this setup than any other I have tried so far, although I haven't done it enough times to know for how long. I think we are doing pretty much the same thing in principal.