I don't think going up to 9's will give you that small an increase. If the measurements of the sweater are borderline smallish, you could go up a size.
Or maybe just knit a little looser.
You have to really decide what you want. If my calculations are correct, if you knit enough stitches for the pattern's gauge to call for 16 inches in width, you could end up with 15 inches.
Anyone else with imput, feel free to jump in!