pwebster2 - If you are getting good smoked food from your smoker, then the smoker is doing it's job. TBS is always desirable, but not always achievable. I have a Cookshack and the initial smoke is opaque but rather heavy. After a while, 30 or so minutes, it settles down and I can detect the faintest wisps of smoke coming out of the smoker for the next few hours. I am assuming that the wood initially used up all the oxygen available and has been reduced to a slow smoldering lump, thus less smoke. In any case, while I worried about smoke when I got the unit a couple of years back, I have stopped the agonizing. It will belch once or twice on occasion, but not much. In any case, I get great ribs and butts from the smoker, and don't have to tend it and feed more wood. Just a couple of ounces at the start and I am done.
AS for adding a tube smoker, I am assuming you are talk about one from Amazin, it will not stay lit in most cases with your smoker as it is too air tight. From what I have read on other forums, users had to drill an additional hole to allow for additional air. They do work well with less air tight smokers.