This is a great opportunity for a creative back design. Perhaps some orphan blocks for the strip or use a strip of coordinating fabric between the 2 butterfly pieces.
Check the selvage direction when piecing.If the selvage of piece #1 is on the left side, the selvage of piece #2 should also be on the left when you sew them. This keeps the print design going. Some prints won't matter if they get turned.
I pin a sticky note to the top of the piece to keep it in the correct position before sewing.