Charcoal Basket:
Any basket is better than no basket. Use it 'til it dies, then buy some 9 ga expanded metal, have it cut to side, and wire your new box together.
Tuning:
I'm just an FNG (Brand New Guy), so I don't know what mods you've already made in terms of tuning your NBBD.
If you haven't put in the baffle and extended the chimney, do those first. Forget moving the thermometer hole. Get yourself a dual probe wireless instead.
After you've got the baffel and the flue, buy an inexpensive metal loaf pan and a full size "hotel" or "steam table" pan. The loaf pan goes on the top rack in the cooking chamber, over the baffel, about an inch from the firebox bulkhead, and is oriented parallel to the bulkhead. Set the hotel pan on the lower rack as a drip pan for the top rack. Stop and admire your handiwork.
Before cooking remove the loaf pan, and put about 1/2" to !" of water in the drip pan. Open the firebox vent and flue all the way. Start a "Minion Method" fire in the charcoal basket in your firebox. When the top layer is burning (about 15 minutes after dumping the chimney) and temperatures are at or nearing cooking levels, close the firebox vent 1/2 way. Fill the loaf pan with hot (or at least warm) water and set it in the cooking chamber as described. Give the pit another 10 minutes for the temperature to stabilize. If the temperature is close to what you want, close the firebox vent so it is only 1/4 open. Give the fire five more minutes to stabilize and adjust the firebox vent to speed or slow combustion to achieve your (more or less) desired temperature. (Use the firebox vent ONLY. Leave the chimney flue open to prevent creosote buildup and to allow ash to escape.)
Move your probes around to check side to side temp differential. Set up this way, an NBBD should run about as well as a Lang. That is, no more than 20 deg differential from end to end. If the differential is greater, move the water pan to the as close as possible to the hottest spot in the pit.
At normal temperatures, between 225 and 275, you'll have to refill the water pan approximately every three hours. Don't refill the drip pan unless you notice a differential increase. The pan's principal benefit is complicating the convection flow in the chamber. The meat grease and drippings should be sufficient, and the water pan will keep the air sufficiently humid.
High humidity serves multiple beneficial purposes. In terms of tuning, moist air has a higher coefficient of heat transference than drier air. In terms of placement, the water pan cools the air nearest the firebox -- where it would otherwise be hottest. Additionally your food will have less tendency to dry, your temperatures will remain more stable, and your food will actually cook slightly faster.
Set up this way, my Bar B Chef Offset -- very similar to your NBBD -- runs a differential <5 deg., from side to side.
Save the diverter/tuning plate material for another project.
To further tighten your cooker, get some wood stove door gasket (the tape not the rope) and glue it around the door frame (2,000 deg glue, not the RTV stuff), to keep from losing moist air from the chamber. Recirculating moist air keeps your food moist and your smoker efficient. Drawing a constant supply of cool, dry air to the fire will dry your meat and burn your fuel faster.
Which brings us back to the charcoal basket. No need to sell you on it because you're already going to do it. But for the record ... The basket burns fuel more efficiently because some of the energy in the hot air on the sides of the basket can make its way into the cooking chamber. Without a basket it just bleeds off the metal skin of the firebox into your backyard.
Physics. Not just for breakfast anymore.
Rich
