I am not familiar with the suit of which you are speaking of, but I would have to assume that since you are talking about sewing up the back of the suit they must already be a seam there. Should be a simple matter of opening the seam the length of the mini zipper that you want to use then sewing one side of the opening to one side of the zipper and then the other side of the opening to the other side of the zipper, Remember, though, that the zipper will make the suit slightly bigger around the middle by the width of the zipper, itself, so you should take that into account when sewing it in, ie take in a little extra material.