I don't mind stacking some coal against the water jacket, it's constantly cooled by the water on the backside anyway. I do notice, if it's touching the water jacket it is loath to burn. I do wonder about going much higher in the front than the mark on the front of the boiler, in the front. This is "unprotected" steel and iron, with a high temp silicon seal... can see the bead. Will I warp that section of the boiler, or burn the seal out?
That picture of the firebricks in the front and the coal piled in behind it... a scream.
How long would that burn in my boiler? Maybe a day and a half? How do you keep the fire from drowning itself in ash?
I don't rake or poke, unless I have clinkers and bridging and can't shake them loose. I rake the clinkers to the top/front and reach in and pick them up... with a pair of heavy welding gloves on...