wow - that's exactly what I want but I'm afraid that pieces 1 and 2 won't match up then...
oh, i see what you're saying. duh.
i would measure the length of that part of the seam as is, then measure it with your alteration.
if the altered seam is longer, then i would add some fabric to the neckline on piece 2 and decreasing the angle of the side seam, like so:
will that work? uhng.. having trouble wrapping my brain around it now.