^ Note that most pros do not use only 1 ball toss -- despite what some coaches will tell you. Sampras has said that he has 2 basic tosses. Elite players will often have 2, sometimes 3, different tosses. However, the difference between those 2 or 3 tosses are probably much less for elite servers than it is for us mere mortals.
You don't need to disguise the fact that you are going to hit your first serve flatter than your 2nd serve. Instead of disguising the type of serve you are going to hit with the ball toss, disguise the placement of your serve.
If u have one foot stuck in yesterday & one foot stuck in tomorrow, u are peeing on today.