Josh (or anyone else),
Do you soak the wood chips/chunks? I used to do this with wood chunks on top of regular coals in a grill. It would work great for a while, but if I was cooking something for more than an hour they would dry, then burn, and I'd lose temp control. I actually was using two grills for a while, always having one in temperature due to adding new, wet wood chunks. It worked, but wasn't worth the effort.