I am a 13 year old using: Wilson Tour 90 3 grams of lead in the throat Babolat Pro Hurricane String-Switching to a softer one when they brake Strung at 53-To get used to weight and low power I am seriously not too muscular(exept my legs) and weigh at 130 lbs. My height is about 5 foot 3 inches On my serve I use a platform stance and a good knee bend. I throw my body weight into the serve and end up about a foot or two away from the baseline after I jump into it. I put some spin on my first and a bunch on my second, but for some reason my power from my serve seems kinda low to me. What can I do to add more power to it?