Firstly apologies for all the posting.. This is my last one. I got the gold medalist!
Level 18 is done by first firing a shot againts the left wall so it gets a good deal of the starts above the see saw before hitting the very rightmost edge of the see saw to tip it ALL the way.
Now place your mouse just to the right of the triple thing and you wont need to move it for the rest of the level. Fire three fairly powerful shots:
The first will get the ball in the bucket and pick the rest of the see saw stars.
The second will tip the see saw back so its out of the way again for the last shot.
The last shot should bounce off the side of the bucket and hit the last star and triple finishing the level.
See pic of one of my failed practices