You're describing a some-what similar situation as I had encountered when my Smoke Vault 24 was new, only I went a different direct to correct my issues.
I bent the tabs on the lower intake vents so I can close them up tight, then added a 24" vent stack, and I run the top vent fully open. This gives me more evenly distributed temps from top to bottom, and temp variances from corner-to-corner/side-to-side are reduced as well. Smoke chamber humidity is much higher, and I use approx. 0.5-0.8 quart of water per hour, with 20-30% relative humidity and ambient temps of below zero to ~70* F. I go through a bit more water at cooler ambient temps, just because of higher burner flame to maintain chamber temps.
My theory on the success of this simple mod is, by not allowing any cool air to enter the smoke chamber through the lower vents, only heated air from the burner housing rises through the chamber, thereby creating less chaotic flow and more efficient transfer of heat. Stale smoke/creosote is never an issue, as I'm compensating for the reduced intake air flow by adding the stack for improved draft through the burner housing.
I run my Vault in this configuration for every smoke, except when smoking/drying jerky. Then, I open the lower intakes to remove the humidity from the drying meat, allowing for a faster dry time with lower temps.
This is outlined in my Smoke Vault 24 Product Review...I know we're talking about different manufacturers here, but the smokers are very similar in their basic design.
Here's the thread:http://www.smokingmeatforums.com/for...ad.php?t=78485