Wait a minute. If you want to INCREASE draw length by modifying the handle exclusively, you' d have to REMOVE material between your grip hand and the riser.
Nope, other way around. By adding material (keeping the same style grip), you will move the riser further from your body. In order to keep the same anchor, you would have to increase the draw length.
If you remove material, you would bring the bow closer to your body, and would have to decrease the draw length in order to keep the same anchor.