I am smoking 4 slabs of spare today on my Horizon 20 RD offset. In the past I have never had a need for rib rack and have always cooked them laying flat. My temperatures are running about 220-230 on the door therms and 270-280 on the Maverick. The fire is smaller than usual and very little wind today as compared to the previous times I have been cooking. Also a drier day (for florida) then I am used to. Question - Could having the ribs laying flat cause a big enough disruption in air flow to cause the temp differneces? I have had the temps generally be with in 5-10 degrees accross all three when cooking smaller amounts.