I should probably add this to the thread as some may find it useful in the future.
In the BBQ with Aaron Franklin series he cooks a lot on the Pecos ,which by our standards is a cheap offset smoker.
I'm a couple of the vids you can see the size of wood chunks he is using. I think this is interesting from a heat management perspective
https://youtu.be/LbzEa_juegs?t=5m53s