If you have trouble generating power when forehand looping, try out these two tips, and you'll be surprised at the improvement. First, keep your legs farther apart. This gives more stability and more torque into the shot. Second, contact the ball more from your side. This forces you to use your whole body instead of mostly your arm. By following these two tips, you'll automatically put more body weight into the shot, increasing your power. If your basic technique is roughly correct but you don't have good power, these two steps will be a huge help.