This is an OpenScad parametric design for a screw based micro adjustable Z stop for the Makerfarm's Prusa I3v. It works great on my machine but if you want to change it just tweak the parameters and recompile in OpenScad to generate the STL.
The pieces are eazy to print. I used PLA and it works just fine. One thing to remember is toenable material support for the two M5 screws head sinks.
I installed it using the stock screws that came with the I3v (cut the end of its metal lever, not sure if it is necessary), M5 screws for the rail slots and a long M3 screw for the adjustment screw. For installing the switch I also used M3 screws and enlarged the hole in the micro switch to fit. A cleaner solution would be to get smaller screws (M2.5?) and reduce the hole diameters in the OpenScad file.
The adjustment screw is positioned to hit the switch near that plastic pin rather than the edge of the metal level. This decreases the leverage and increases the stability and accuracy. If you interested in a more accurate switch, search digikey for snap action limit switches with low differential travel but the stock switch of i3v works great for me.