In Level 8, you get 5 but only need 3. Check out the video, we get 123370 and 3 stars.
First send Red straight ahead to topple the stone tower and upset the little piggie there. Guess he should have gone to market! We send Bomb Bird to the middle of the lower wooden support protecting the cave and the blast has causes some significant damage. Finally, Matilda goes slightly lower, bombing the remains of the toppled tower and ricocheting into the upper right of the cave, taking out the remaining two piggies that stayed home. Wee Wee Wee they scream!