There is a Collectible Item hidden in Angry Birds Star Wars II Reward Chapter level PR-7 (Zam Wesell), under the slingshot platform. Toss Zam backwards, grabbing the platform with his grappling hook. This will swing him back around toward the Bonus Box.
Go back to the Complete Star Wars II Bonus Boxes Guide. If you have a different strategy feel free to leave a comment below.
Zam is female … it should be her grappling hook, not his ;)
It also works to fling Zam diagonally down and grab the platform to swing underneath and hit the bonus.