I too have a BSKD, and had a hard time regulating the heat. My big problem was being able to get enough heat in the unit during the winter months.
My first mod was a baffle to get the heat under the water pan. I did one very similar to the picture above, but I made it out of 1/8 plate steel, and made so that it could bolt in with the existing bolt holes (longer bolts are needed). This really helped even out the heat of the fire box. Before this, you could have almost 100 degrees difference from one side to the other.
The second mod, was kind of hack, but I need something to insulate the cooking chamber. I took some ½†plywood and lined the outside and top of the smoking chamber (I had it laying around). I then took a heavy duty beach towel and made a “blanket†to go over the front door. This way, the whole cooking chamber was insulated. This made a huge difference. Iâ€[emoji]8482[/emoji]ll go back and make this proper later, for right now it looks bad, but works well.
The next mod was a removable baffle that drops in place of the cooking grate. A piece of 1/8 tread plate with a some angle iron welded around it, and another piece of tread plate welded on top of the angle. This created a ½†air gap between the tread plate pieces. If you just use a single piece of steel, it helps, but the heat transfer pretty readily. With the double wall construction you insulate the top very well. I then put some handles on it so I can remove it easily for clean up and in case I needed to tend the fire from above.
After that I double walled the inside of the fire box (the sides, bottom, and the piece of wall that is under the opening going to the cooking chamber). Used some 1/8†plate. Left about a ¼†gap between the plate and the side walls with vents at the sides to pull air past and remove the heat from the 1/8†plate (you want a diffuser/insulator not a heat sink). You can now hold your hand on the outside of the firebox when the temp in the cooking chamber is 230. Before it used to burn the paint off.
I have two other planned mods yet.
The first one is to figure out a way to get more air at the coals. It needs exactly what Bob-BQN showed. Iâ€[emoji]8482[/emoji]ll probably just scrounge for some heavy-duty grating and copy his.
The other mod is to add an additional heat source for winter use. I was thinking of putting a electric or gas element under the cooking chamber to add a few BTUâ€[emoji]8482[/emoji]s for when itâ€[emoji]8482[/emoji]s near zero or windy out.
One very important thing to realize is that the front door temp gauge is just about useless. Iâ€[emoji]8482[/emoji]ve “mapped†out the inside of the cooking chamber with a wireless probe and can tell you that the temp is very even across most of the chamber. When you get within an inch of the door/outsides, it acts as a heat sink and the temp drops. Usually the door gauge will read 30-50 degrees lower than actual center temp. Anywhere else, the temp is very even. I now use a mechanical gauge and a wireless probe that measures towards the center of the cooking chamber versus the door mounted one (one gauge is near the bottom center, one is near the top center).
Overall, I can cook some decent stuff with the unit, but the overall construction seems kinda shoddy. If you feel like tinkering with it, you can make it pretty nice.
Brett