After the grilling session was complete, I decided to try choking down the intake to see if I could throttle back the temps even without the ball valve in place. After adjusting the intake to 4 rows of holes, the Shorty happily ran at 300 degrees. After an hour, I choked it down further to 2 and a half rows of holes, which resulted in a stable temp of 250 degrees and I put some sausages on for a couple hours.
Just to ensure that these results were not influenced by dropping ambient temperature outside or lack of fuel (and after I took the sausages off), I opened the intake slide vent back to half and after about 15 mins, the Shorty was back at 400 degrees.
Overall, I am very impressed. I did use a couple online calculators (with some fudging) to figure out the smoke stack height based on the diameter of the pipe and the volume of the Shorty. It seems that the size I used is the exact right size to allow for temperature management by intake only. I still haven't purchased a plug to screw into the flange when the session is over, so I simply used a high heat glove to screw out the stack and screwed in the ball valve to close off the Shorty to shut everything down.
During both sessions, we had a fair amount of wind, but unlike the previous tests, the Shorty with the stack was completely unaffected by the changing wind directions or speed. Simply put, it just held constant temps. It is important to note, just like any drum smoker or similar, if you open the lid for more than 45-60 seconds, the additional fresh air will cause the fire to kick-up, but it quickly goes back in just a minute or two after closing. That said, you obviously can't leave it open for long as I would imagine it would take longer to cool back down to the desired temp.
All of this being said, I'm strongly considering implementing the same flange and setup on my full-sized Oklahoma Joes Bronco Drum Smoker. In the meantime, I am overwhelmingly surprised by and happy with how the 'Shorty' version turned out. I'll update as I do some other cooks in the coming month. :)