It might not make it much wider, possibly an inch. Try it on the larger needles for a couple inches, see what it measures. You could add more stitches, one on each end (2) for k3 instead of k2, and another 2 on the edges of the cabled panel for a total of 4 more. That and the larger needles might get you a couple inches. Play around with the pattern on scrap yarn, adding the extra stitches so you can take notes of what you should do with those in the cable panel.