I picked up stitches over the back and two sleeves, leaving the top of the lace panel alone. Then I worked ribbing in short rows. The ribbing slopes down nicely to the front two raglan lines where the lace starts, and pulls the neck in just enough. It's still an open, summery feel, but now I'm not worried about my bra straps showing, let alone my entire shoulder.
p.s. I should have straightened up the lines of the sweater for these pictures. It's not really all slanted and off-center. Sorry about that.