[David]

You cannot reach back and grab the ball once you have passed the finish line. This would violate the "you cannot cross a plane you have already crossed" rule (i don't have my manual handy, otherwise i'ld give you the number and exact wording). The only way around this is to hit the part of the ball that extends past the finish line (its not a big target). It is much easier (and less likely to break a rule) to hit the ball from underneath (which is legal) or grab it from behind.