I have wanted to try chunks for a while but I have so many chips I dont feel like getting chunks. I add every 30-40 min like werdwolf. I always watch my MES closely because it has a tendinsy to smoke too much right when you put in chips then smoke too little after they burn heavy. I probably should try chunks though considering I have been putting charcoal in the wood tray lately.
I've used chunks of maple, about 1x2" and found they generated smoke thicker than I wanted, so I wrapped the wood in aluminum foil and put it in the tray. Started off nicely, with the foil slowing down the smoke production, but after a while it ended up accumulating the gases and they would 'whump' as they went off, gathered more gas, and when 'whump' again every 30 seconds or so.
So, I put a couple of charcoal briquets in the tray to get a smoke ring going and feed the wood chips about every 45 minutes.
Could be a project called for here, an auger style screw on a clockwork timer would work. But then again, I wouldn't have an excuse to hang around the food all day babysitting it