I too have experienced some uneven burning, more directly, the center of my lump becomes too hot. I am doing some wings and decided to lay a larger piece of lump directly in the middle of the box once I got up to the temp I wanted. This seems to be working, evenly distributing the heat, while not giving it too much of an indirect cook.
Thought I'd share. I'm wrapping the wings in foil and placing in a cooler layerd with towels fresh out of the dryer so I can retain as much heat as possible.