I use the Sono 2 pounder. My experience with the recommended load, 2 cans, is like posted here. Some varieties are slow to agitate resulting in 10% charred beans. Worked with Sono to try to resolve the problem, their concern was my elevation was 6500' (we look down on Denver!). First we removed the metal collar around the fan intake with no improvement. Next we turned down the gas mixture, quarter turn on the valve (accessed on bottom front) until the unit was continuously heating, with no imporvement. I was trying to get a prefect roast at maximum capcity, I could always load less and achieve this. In the end, when I quit trying to find the solution, I found comfort with a 1 1/2 can load for the problematic varieties. I have started to use weigth rather than volume, but not enough data yet.
I do have a question for other users: I get dust and chaff that somehow blows out over the machine and immediate area. I've checked all joints and sealed well I believe. Is anyone else experiencing this? Is it normal? Thanks.