Where the "B" measurement says to add 7/8", most of us add a full inch. Gives a little leeway for trimming. Other than that, figure the dimensions as given without adding more leeway. This is my "always" method! A tip when trimming- I have a ruler with a triangle that intersects at the 1/4" mark. Lining up the ruler on your FG allows you to have an exact 1/4" seam allowance at the top. Then measure down from that intersection for the desired "B" measurement remembering to add for the bottom seam allowance! In the pictures mine has already been trimmed, but I often find it necessary and am thrilled I discovered this way!
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