Here is my modified Brinkman SnP. It's pretty much on its last legs.
I put in a baffle between the firebox and the smoke chamber. Picked up some 16 or 18 gauge steel from a local supplier. Cut out the piece with my cutoff wheel. I made it wide enough to span the diameter of the smoke chamber, then angled down the sides to kind of follow the countour of the chamber, until it got down to the level i wanted it at. I had to make two 45 degree bends with it. Then I just cut two other pieces the same width for tuning plates, and spaced them out in the bottom of the chamber.
In this last shot, you can see another tuning plate, and the flashing I used to get the chimney down to the level of the grate.
Before I did this, I had temp swings of 100 degrees from end to end. After doing this, I have a temp swing of 15 degrees. Highly recommend doing it. Pardon my dirty pit. Haven't cleaned it out in a while.