Well, I didn't have a lot of success with regular charcoal over the past couple of days so I changed gears and tried lump. Fired the UDS at 530pm last night and brought it up to 240ish around 615pm and started the clock from there. From 615pm through 1130pm the temps did nothing from slowly drop regardless of what I did. Here are the pictures of the lump this morning after I pulled it out of the UDS. As you can see I didn't use a great deal fuelwise, but the lump basically burned straight down and didn't ignite any of the surrounding fuel. This was fired in #5 which is a DOT approved 55gal drum, three 3/4 intakes of which two are capped and one has a magnet over the opening. I had set the magnet at half and capped the other two when the temp hit around 220 and the basket which consists of expanded mental formed to a weber 18" charcoal grate sits 4 inches off the bottom. Bear in mind I was in fact able to hold temp for about the first hour and after that is when it did nothing but fall. CONCLUSION: Cowboy lump ISN'T a quality fuel for use in UDS style cookers, however, let it also be known that as far as lump goes, Cowboy lump does live up to the expectation and produces very little ash as shown in the second picture. I will continue to run tests this weekend with Kingsford Comp and RO lump and post those results as well.