I am planning on building my first UDS. I ordered a Big Pappa Smoker Kit for most of the parts but want to make some modifications in order to improve the efficiency of the unit. My main concern is that the air inlets on the bottom of the Big Pappa Smoker kit are sliding units (similar to the top of a webber) and I imagine that they are not very air tight in the closed position. I notice that most of the custom build UDS's use ball valves, which I imagine make it easier to adjust the precise amount of air let into the unit. Do you think its worth using ball vales instead of the sliding units that come with the Big Pappa Smoker kit? Also, any additional modifications that you all might be willing to recommend would be greatly appreciated. Thanks.