got a chargriller and Im proud to say I finally mastered the temp at the end of the time I was using it regular. First off, The fit between the firebox and main chamber is terrible. I used some high temp stove caulking to seal it. Next, everything else on the whole smoker will still leak, you just have to accept this. The ash pan drawer on the firebox will get hot and it will expand and not seal. If you notice it fits pretty good cold, let that dude get hot and you will have a gap. The whole main chamber leaks around all the sides. My method was this..first I build a charcoal basket. Made it out of expanded metal. Believe it was like 12x12x8 or so? Next I flip the charcoal pan over so the grates are facing down. I usually hung it to where the top of the arch was just covering the top of the firebox opening. This will help act as a baffle so all your hot air gets distributed more evenly. I sometimes put some foil in the gap between the upside down pan and the firebox but found that the side opposite would get much hotter. (i have dual thermos on mine). Usually I just left it hanging with no foil. I also would put foil all around the outside lip of the main chamber to help with the air leaks..it will still leak just not as bad. My method was to fill my basket darn near plumb full with unlit and throw a whole chimney of lit on the side CLOSEST to the cooking chamber. If you put it closest to the air intake it will stoke it more and get hotter. I usually ran my vent about 1/4. Im talking I would just barely tap it with my spatula so where there was a sliver of opening. The damn thing leaks so bad its like you have it half open. This would run 250 for about 4-5 hours before I would have to refuel or add chunks. These things eat fuel, thats just how they are. Sorry this was so long
matt
EDIT..i know you will read all about the chimney extensions to where you bring the stack down the the exhaust. I cant say if it helps or not. I had one on mine, but I also ran it without it a few times and never really noticed a difference. The only thing I do know is it would sometimes hit whatever I had on the grill. Due to this I would take it off because I needed the space where it was sticking down. Most of the time I left it on just because I had no reason to take it off. If you want to try a super simple way to do it, go buy one of those BIG monster or energy drinks, cant remember which one. It was called like the BFC (big F/n can) or something like that. Its like a 30 oz can. Cut the ends off of it and it slides right over the exhaust stack. I used to hose clamps to cinch it down.