I have been BBQing for several years now, I started on the Brinkman vertical and a few years ago I upgraded to a ProQ excel 20. I have managed to overload my ProQ dozens of times and now it is time to upgrade. A few months ago, I designed a horizontal pit using a 250-gallon propane tank with the firebox mounted on the lower rear. The cook chamber was going to have a convection plate in it with half the calculated opening on each side and the smoke stack in the upper middle. Then I discovered dual wall and insulated designs for the firebox and the cook chamber, not sure about the simplicity in creating an outer skin for the propane take I held off. Is there an issue with only the firebox being dual wall and insulated but not the cook chamber? Last night I dreamed up this design for a horizontal please tell me what you think about either design. 78-inchs tall, 36-inchs wide and 24 inches deep cooker/26 inches of the length would make up the firebox. The bottom 8 inches of the firebox would be an ashes area and air intakes. Above the firebox will be a 1/2 in convection plate. (I don’t know if 1/2 inch is the correct thickness). A water pan might sit on the plate. There will be 3.75 inches on either side of the plate running the width of the smoker giving me 180 square inches of firebox to cooker opening to allow heat and smoke to enter the chamber. I would allow for that same 3.75 inches between the sides of the cooking grates and the inner skin so heat and smoke wont get trapped as it is traveling up. I am thinking for the inner skin 3/8 inch steel and for the outer skin 1/4 inch steel with an unknown type of insulation between them. I am thinking having slots for 7 grates but building 6 so I have room for turkey and bone in prime rib or adjustments for any type of food. The grates will have some sort of shallow pan under them to keep fats and rubs from different meats off one another. I am considering three thermometers in the door to check for heat variations in the chamber and one in the fire box to monitor that temp also. This cooker will be mounted on casters and I am considering also welding a dolly to the side of it. I am hoping to use the 78 inches in length in a single sheet to reduce the amount of cutting and welding. Please let me know what you all think and I hope to see you all at an amateur competition soon.