Lesson Learned # 1, the 350X350mm feed shute is too big. Next one will be 250X250 Max
Lesson Learned #2, the hot Gas Out let to the Cooking chamber is too big, heat is very hard to control. Solution is to install a damper between the fire box and the cooking chamber to get it set right then lock in place. Use cross section area to determine best size for the next one.
Lesson Learned Number 3, Hot gas outlet is too high up in the the firebox, should be about 25 to 50 mm above the ash grate.