I'm in the same boat but I thought I would follow a similar plan to the geoff thomas smoker I already have. It's dying through rust but is a good size. The "firebox" is a wok burner under a plate that I throw handfuls of sawdust on. It works OK.

A question for you all - do you prefer hanging the fish vertical or laying them flat. I find that laying them flat means the fat and water that comes off the fish doesn't run off and its easy to get them mushy. I had an old dryer in which the fish were vertical and it was fantastic. The GT smoker has them lying flat on racks and the results with it have been mixed, some good some awful (mushy). Im thinking of recreating the GT smoker but with racking so that the fish will hang vertical.

What do you others think?

ZG, mine's a cabinet dryer mounted on top of an old kent fire box. I have no problems regulating amount of smoke or the heat for that matter. Once I've got the fire going and the right amount of smoke is being generated for a colder smoke just shut all the damper vents, as the cabinet is directly above the fire box I still get a certain amount of heat but the resulting time to smoke has still been between 12 and 18 hours. I perfer a hot smoke as I cant be bothered waiting 12 or more hours when your fish can be ready in 4.

Yah, that photo was taken in the very first part of the smoke. Once that has been established, the fire is kicked out and the embers smould away, and the ventilation is minimised.

Still havent found out what the doors are made of, but will email the old man tonite to find out.....

I am not entirely sure, but the door is in two parts, with a bottom section that goes to about the metal plate just above the fireplace.  This section has ventilation holes that can be closed or opened as reqired.

The doors themselves are really heavy, and metal plated, so I think it is obvoiusly some sort of fireproof material.

I can find out for sure for you if you want??

Yah, the heads are very tasty! 

I am sure he could come to some sort of agreement with you....  probably over the exchange of a few Lion Reds!

It is an excellent smoker that he built himself.  The smoker when new was not as good as it is now.  It is strange, but the more you use it, the better "seasoned" it becomes, and the tastier the fish are.