I've used the placket pattern from David Page Coffin's book and love it! It is flawless. I have altered the pattern slightly to increase the seam allowance. This helps me in two ways: 1) it's easier to turn under 1.25 inches rather than 1/4 inch, and 2) the seam allowance acts as an interfacing to give the placket more body. I alter the seam allowance on the 'right hand' side (the one with the #6 fold to 1.25. The 'left hand side' I increase the seam allowance to .5.