Love the fabrics, and your calculation method is spot on, especially including automatic stash building in the calculation. When I sewed clothing, I used to take anywhere from 1/4 to 1/2 yard off the pattern envelope requirements, because my mom said they always had a layout that wasted fabric and you didn't ever need that much. Now I use your method---calculate the fabric requirements, add 4" for shrinkage and off grain cutting at the store, then add 1/4 or 1/2 yard just to be safe.