Round 1: Go down to the last peg, drill down - 10,100 points
Round 3: Go down to the last peg, drill left - 7,000 points
Round 4: Go right to the middle peg, drill up, drill down - 7,000 points
Round 5: Lure the baddies all the way to the right, go to the left peg, drill up - 10,000 points
Round 7: Build a maze on the right side of the island, lure all baddies in, finish them off - 20,000 points
I build the maze like this and finish them off by drilling up at the top peg on the left.
If you miss one baddie, you get 15,000 points.