Ok, some pics of the smoker so far:
First the fire basket. I picked this up today, and already need to take it back. It was dimensioned to fit inside the lid of the firebox (see below). I modded the specs on the lid, and forgot to send them new dimensions for the fire basket. It will need to be one inch narrower. As it is, it is 16"x20". It will have to go to 15".
Now the firebox. It is 18"x24" and 18" deep. I picked up the lid today. It is designed so that the plates (1/4") slide into the angle which will be gasketed to seal the plate in when in place. The large plate is 16" and the small plate with the handle is 8". The small one will be fitted with a lip on the side that it meets the large to seal that joint when in place. I will slide the small out to add fuel. I should be able to keep the fire in a 16"x15" portion of the basket covered by the large piece for the short time the small plate is open.
More pics to follow as progress is made!