Bad Piggies Rise and Swine Bonus Level 2-IX (2-9) can be 3-starred using two contraptions, each with three boxes and a boxing glove. To avoid Krak-Snap, face the boxing glove rightward and use it when the cart reaches the wall at the bottom of the hill. This will push the cart back down the hill to the finish line. For speed, turn the boxing glove around to blast the piggy out of the contraption.
If you have a different strategy for completing this level feel free to leave a comment below.