Hey Mike,
As others have said, don't worry yourself with empty box temps. Without a heat sink from meat in the box, the temps just fluctuate too much. The heat sink helps even out the temps.
With meat a D model or one with an external Auber controlling the element should settle within 1-3 degrees, while a standard (non-D) smoker can have a range of 20-30 degrees. This does not affect the smoke at all.
Also, note that the heat toward the top of the smoker will be the most even. It stands to reason that the heat nearest the element will be a little hotter and will not be as stable.
I often time do not even bother with a box probe anymore. Smoking is not an exact science. I challenge anyone to choose between the results from a D Model smoker and a standard version with the temp swings. It just won't matter. The only exceptions would be some some meats like fish and jerky where a swing too high could negatively affect the results.
It is not a question of "more meat increase the setting". It is a question of empty box vs. a box with meat in it. I know my temps are within the range no matter whether I am smoking poultry quarters, butts, or even a packer brisket.
Some (non-D) smokers tend to run a little hot or a little cold and there is a temp control knob adjustment instruction guide on the Smokin-It website. But, most don't have to worry about this because they just get a feel for their smoker and adjust the temps accordingly. My smoker never needed any adjustments and if I want a smoke to average 225, I set my knob at 225 and walk away or even go to sleep for the night.
Now get some meat in the smoker, set to the desired temperature, don't sweat the swings, and then enjoy the results!