I've been trying to get my serve so the ball hits the back fence off the first bounce and I can't get the darn thing to do it. I have no idea how fast my serve is, but I do hit aces and unreturnable serves occasionally against high school players that are upper JV and lower varsity. That makes me feel like it's not that I'm just not advanced enough to hit the back fence. Any advice on how to accomplish this? I know more topspin would help. anything else?