ChrisPer: Yep, sounds about right...the propane system I was running before was very difficult to control and I was watching it like a hawk too. The temperature variation is a problem too, if it comes only from one direction the charcoal near there will overcook. Which is why the temperature in the kiln I use comes from all around. In the kiln there is a gallon can and centered in that can that's where I have the small paint can that contains the charcoal.
I raise the inner cylinder (small can) off the bottom with a folded shelf made of sturdy screen. This way the hot air circulates all around the inner cylinder evenly. Another important factor is thermocouple placement, if the thermocouple is in the center of the inner cylinder, the heat will rise above the target temperature on the outer edges before it rises to target in the center. However, if you place the thermocouple on the side, near the metal of the inner can and inside the inner can, you will regulate the temperature as it enters. With time, the temperature will even out and cook everything at the same temperature. Hope this helps.