Rancilio says 14g yields 3oz in 15-20 seconds. I returned to the spouted portafilter and tried 16g and a yield of 2-3oz in 15 seconds. I jacked the stopwatch of the first one but achieved zero channeling as far as I can see (photo above). I pulled 3oz. My second shot also resulted in zero channeling, was on the upper end of 16g (there was some water leakage due to being too full), and 2oz including crema. This was the better shot. As for my milk, there is little screaching but I’m still not achieving microfoam. 

Here’s my third try today with decaf:

17g in the portafilter; scooped out to a reading of 16g. ~2oz in 15 seconds. There was some channeling on the right hand side. Espresso tastes better but not quite there.