finished sweater is too WIDE. What can be done?

[carolyn100]

Although I matched the gauge and followed the NORO pattern for my size, my finished pullover sweater needs the side seams taken in by at least 5 inches at each side of the bottom and tapered up to the armhole. It's in stockinette. How can this be done gracefully? The yarn is 40% cotton, 30% silk, and 15% each