The better way to shoot a lighter arrow is to go to a different carbon fiber. Pay attention to the grains per inch of shaft length and select one of minimal weight and you'll have the best of both worlds (low arrow weight and forgiving set-up). That being said, with your longer draw length, you already have a speed advantage by your increased power stroke. The increase in draw length should overcome the increase in arrow weight as a relative comparison. In any case, I'd recommend against the overdraw. Shoot the longer, more stable, more forgiving, heavier arrow with more momentum and hit what you're shooting at. Speed doesn't kill, accuracy does.