A pro once told me that the toss is a myth. Meaning no one has a perfect toss. He said having a "good toss" is really about being balanced throughout the service motion. The thing that really helped my balance on serve is the "squash the bug" technique. Meaning starting with the weight on the back foot, when my tossing arm goes up I twist and "squash a bug" with my front foot, weighting the ball of the front foot. Added so much consistency, and mphs to my serve.
Look at Ryan Harrisons feet in this video hitting serves: