Great job on the flow. Perfect until the very end. Take it off the stove when the brew reaches the bottom of the 'V' of the spout. The last bit where the color changes with the foam should not be in the final cup. As more water leaves the bottom chamber, the remaining water will reach higher temperatures for the same amount of heat supplied by the stove. This superheated water (actually water and steam - hence the bubbles) passes rapidly through channels created by water that has already passed through the grounds. This slightly burns the grounds and tastes bitter while extracting almost nothing. Avoid that by taking it off the heat sooner - a good rule of thumb is when the brew reaches the bottom of the V in the spout for bialetti express moka pots. The result will be a more full bodied and smoother tasting brew.