Nice UCD. As for the throws, be sure your surfaces will move farther by disconnecting the linkage and moving them by hand. Sometimes if they are hinged to close to the wing it will limit their movement. As long as they have more throw available, have you maxed out your servo's throw? If available on your radio, you can increase your ATV or similar parameter. Obviously you should be using your outermost hole on your servo arm. It's best to try and stay near the outer end of your control horn as well to help minimize slop in your control surface. This will lessen the chance of flutter as well. If you've done all this already, then longer servo arms are the next step, which I believe was your original question. Are you using a two-stroke?