Update 2016-01-08

Update 2016-01-08: The WHO report I used gave numbers for soy protein (6.48%) but not black bean protein, and I assumed it was similar for all beans. Finding a source that gives data for cooked black beans, I now see they're 6.86% lysine, scoring 152, which gives us w=8.5oz and b=1.7oz, but doesn't change the bottom-line 4:1 approximation.