Created another solution for level 19 (Back and Forth).. pretty happy with this one
http://fantasticcontraption.com/?designId=212247
Edit - improved it -
http://fantasticcontraption.com/?designId=212564
Edit - another solution for the Stars level (this idea I got from someone else) -
http://fantasticcontraption.com/?designId=222835
Edit - and my solution for the level called Awash.. put this on hold for a while because it's annoying
http://fantasticcontraption.com/?designId=223308