I copied your design. It worked well like yours until the fire lighter in the bottom of the chimney went out. Then it wouldn't draw at all. The air and fire burned up the feed tube. To fix it I extended the chimney by 500mm and put an adjustable cap on the feed tube. Then it worked really well. Do you have the same issue when the fire lighter goes out or do you keep one burning in the bottom of the chimney all the time. Thanks for posting the video. The grill makes great grilled cheese on toast really fast. Thanks from Shane in Australia.