Okay, I've heard folks like Brad Gilbert discuss this - never gave it much thought until I was watching the NY Open final with Reilly Opelka serving on match point. He tossed the ball up and got a read on where his opponent was guessing. He hauled the serve back in. Next toss, ace in the opposite corner. With serves getting bigger and bigger, I'm coming around to the notion that this should be a fault. Thoughts?