Basic adjustable Z end stop.
The lower is pretty self explanatory
The upper gets a nut pushed into the hex on the underside.
Then put an allen head bolt through a spring and thread down through the top and nut.
I used a spring off an old Weber carb, but any hardware store should have something that will work.
The spring holds everything tight and holds the adjustment.
It's a good idea to make sure the end of the bolt is perfectly flat so you get the expected adjustment.
Added z_stop_low_short. This is 4.5mm shorter and to be used with my brackets http://www.thingiverse.com/thing:1457449