This is my smoker that I built and I can't control the heat. I have done 6 test burns and cannot keep it at the 225 degrees mark. Even if I shut down the damper, it will continue to rise. I started with a 4" flue and my damper is 4"x 9", they are on opposite sides to allow for good transfer of heat and smoke. I thought the flue was not dissipating the heat enough, so I went with a 6" flue but it helped just a little. I have looked for leaks by using a smoldering piece of paper going around the doors and the box but all seems fine. The box is 45"x 30"x 22" (inside dimension) double walled 5/8 plywood with 1"x 3" frame laid flat so my walls are 2" thick. I had extra plywood and filled all the spaces between the one by threes creating a solid wall and roof. It is wrapped with sheet metal, sealed with food grade heat resistant silicone (red stuff), high temp gaskets on box and doors. My firebox as you can see is the minion method. It is 20"x 14" x 7" high. After my first burn I realized that the dividers did not extend far enough to the other side allowing for the fuel source to ignite to soon on adjoining sections creating more heat (I think, sounded good). So I extended them a few inches. I welded 1x1 square tubing onto the bottom of the fb so the ash could fall through and keep the burn section clear. It seems so simple, light a few briquettes, add to the loaded firebox, open damper halfway, fully open flue and as the heat starts to rise start closing the damper until you hit your temp. right? I leave the flue fully open. I am retired and living the past 6 years in Mexico on the Sea of Cortez and the one thing that I miss is good BBQ. Here they just put meat on an open grate and fire up the mesquite. No pulled pork, brisket, sausages, the basics. So in between my fishing, I started this project thinking it would be a piece of cake and I would be enjoying good smoked BBQ. Went up to the states over Thanksgiving and bought back all the Lump, Briquettes, Apple, Cherry, Pecan, Alder, Hickory I would need before my next trip North. Any help/ideas would be appreciated. South of the Border smoker.