start with fewer lit coals. I only start about with about 10-12 briqs. I watch the temps as it starts to rise after adding the lit coals. If I plan on cooking at 250-260, I cap one nipple at 200. I cap the second nipple at 225. At 240, I close the ball valve about half way. Most of the time, mine will then settle in between 250-260. If it goes past 260, I'll nudge the valve closed a little more. If it stops short of 250, I'll nudge it open a little. The key is to start with a small controlled fire & catch your target temp on the way up. If you get too big of a fire mass, you will be wiggle that valve all day trying to get it under control.
I will add this. my drum did like to continue to creep up in temp until I used some red RTV silicone around the lid. However my lid did let quite a bit of smoke out until I sealed it.
Jim Sewell -- GBA Vice President, Master Judge, Contest Rep & GBA Webmaster