Originally Posted by Pappy
I thought I saw one on here before. Someone used the bottom for the top.
I put the bottom on the top. I named her "Bottom's Up" I also made another UDS and used the lid of the kettle for that one. I no longer own that one as I made the mistake of taking her to my son's house for a BBQ and he adopted her. I could not think of a name for her anyhow.
So I ran these smokers side by side with the same kingsford blue. "Bottoms Up" ran at 250 with one and a half bottom vents open. The one with the regular kettle lid ran with three and a half open to hold the same temp. Guess I should have mentioned they both have four 1" bottom vents. It is also complicated in that I think I am one of the few who uses a water pan in my UDS It is a big one at that, 20 quart so I am heating a couple gallons of water also. I have used my UDS for lots of cooks so I am confident to say I think you will benifit from the additional exhaust holes. I have yet another UDS that I originally put a home made vent on with 4 -3/4" holes I went back and changed that one to 6- 3/4" holes.
It seems to work well for me. Here is a picture of the unnamed UDS
I like to think having the exhaust holes in the center and the large water pan as a defuser creates a nice even heat. Love to think about all of this stuff. In the end what is the big deal if your extra vent is not necessary you could still use it to evenly split the exhaust. Also the kettle bottom will not fit the drum like the lid dose. No rocket science here I used an open head drum and pop riveted an alum strip around the inside to create a ledge for it to close on.