Most pro's cannot disquise the flat first serve from their heavy twists.
But you don't have to! The flat first, used in conjunction with a moderate bouncing topspin serve, and a slower, much bouncier twist, is used at DIFFERENT times for different situations.
And if you still insist on BobbyRiggs shenanigans, you can toss the same, then move your body under the serve in different ways to achieve the different tosses required for each serve.
Opponent is watching from the front, can't see in 3D and delineate the difference. And he's watching the BALL.