You can keep the same draw length by twisting both the string and cables, and raise the draw weight a bit too. Problem is, twisting the string and cables puts more pre-bend on the limbs andthat will shorten their service life somewhat. Italso increases your brace height and that practically cancels out any speed gain you might have gotten by the extra draw weight. You wind up working harder for absolutely no gain. If you are really determined to go with more draw weight, the only practical solution is, as others have said, gettingnew limbs or a new bow.