I love my Amy jumpsuits (you can see them here
(bw print), here
(black linen), and here
(navy sequin)) but they all share one problem... the straps just won't stay on my shoulders.
So on my latest Amy, I made the straps cross in the back.
This was a bit of a trick, I went through several bodice muslins trying different solutions to get the straps to cross with a minimum of gaping in the back. But in the end, I decided the best solution was the simplest. I made the straps longer, and attached them so that they followed he angle of the back bodice coming from the armpit. I also removed about 1 inch from the top of the bodice at the center back, grading to nothing, and adding that inch back in at the side seams (1/2 inch on each side). I did this all on the pattern, so that when I cut the center back stripe would be on-grain.