Sumbitch. Thanks fellas. I have some experimenting to do. I don't have a mountain of wood yet, some hickory though thanks to parrothead.
What I've done so far is: Toss in a chimney of hot lump, then a couple of chunks on the hot coals. These first two chunks aren't prehreated though so I wait for the white smoke to tone down a bit before adding meat. Meanwhile I've got four more chunks on top of the firebox getting nice and hot, while starting another chimney of lump. (I've never heard of putting lump on cold, however, I'll have to try that. Hopefully, doing so will prolong holding the desired temp range.) Usually, when the vertical approaches 10-15 degrees from the lower end of that range, I start another chimney. When its ready to go in the firebox, so does two preheated chunks. Then I go in the vertical to mop/mist. Normally, these two actions combine to take the vertical's temp down to a temporary 130-something. The temp comes back up pretty quick thanks to the mods, which by the way I'm successfully using a stainless steel cookie sheet (14 x 16") which covers all but about an 1 - 1 1/2 inch of the left side of the smoke chamber. Square inch-wise the gap is only a tad bigger the chimney opening. But I digress.
Usually this method means that I'm dumping in new hot lump every 45 minutes to an hour depending on the weather. After about three hours of cooking, I discontinue the wood chunks because I've read that meat stops soaking in the smoke after that. In my experience, while I am using the chunks I get longer continuous burns, so I figured that a partial log or actually chunks cut from splits would really prolong having to refuel. Besides, each que I'm using about 2/3 of a 20 lb bag of lump. Now I don't cook as much as some of you guys so the cost isn't really a major issue, but damn, I hate seeing the fuel burn away so quickly.
Anyway, this thread is a keeper. I'm going to print this mutha and stick it in my Brethren info binder. Thanks again.