I added a second rack to my UDS and cooked chicken and ribs for Mother's Day (Sorry no Qview). I had the Chicken on the bottom rack and the 3 racks of BB's on top. I noticed for the first hour that the temp differences from top rack to bottom were 50-60 degrees off. I had about 10 chicken leg 1/4's on the bottom rack and had them spaced with room in between and couldn't get the top rack to get above 200...at that rate we wouldn't have ribs. So I took off three of the 1/4's and freed the middle of that rack up completey so the heat would rise to the top. At that point the temps evened out and were within 2-3 degrees from then on. Does this sound about right when using 2 cooking racks? I also don't think I'm going to foil ribs ever again on the uds. The foil created more pullback but it's not worth the hassle. It seemed just when the UDS was in the zone I had to open the lid again. I had temp spikes over 300 when trying to get all that done and even worse when I had to move the chicken. By the way the ribs and chicken were good. It was the best chicken I've cooked. I used the Travcoman's Slaughter House brine, I think that was the deciding factor. It cooked for 5 hours and was still moist. Sorry to ramble just thought I would pass along my experience. I love the drum just got to cook on it more to learn the tricks. I'll be doing some butts for memorial day and will post pics of that cook. If you've read this far down, Thanks.