Planning my firebox for my smokehouse. I plan on making the outside of the firebox 24x24x24" with the inside being roughly 16x16x16" when all said and done with firebricks, etc. I plan on using a grate to help elevate the fire up from the concrete slab. Would my idea of utilizing the ash dump vent and door work okay, or do I need another vent? If I use the ash dump vent, does the door need a vent? My other thought was to use the door that is attached, but for the to work properly how would the height of the grates have to be in relation to the vents right below the door?