I have upgraded my RapMan with a heated print-bed and needed a modified z switch holder. I tried Laszlo's one, it works, but I had problems with it. It is attached to one of the 3 screws the print bed is hold by. These 3 screws are equipped with a spring mechanism, allowing the print bed to back down if the print head by error tries to go down below the print bed surface.
When attaching Laszlo's z switch holder, this spring has no effect any more. Laszlo says he doesn't have the problem and I think the reason is that I have a RapMan version 3.1 while he has a previous version. My RapMan z stage platform has threaded holes for the 3 screws I was talking about which seem to be the reason for problem.

Anyway, I designed a different solution, where the z switch is not attached to the print-bed but to the z stage platform instead. This also makes fine-tuning the print-bed/extruder distance easier. You can do that with the 3 screws now and you get direct feedback about the new distance. Before you had to turn the distance screw at the print head and run a home sequence to get the new adjusted distance.
With this new mechanism the z switch is not pressed directly, but there is a arm which presses it. The arm reaches up where the distance regulation screw comes down during the home sequence.

Some photos are on my blog:
http://blog.gagalabs.com/modified-z-switch-for-the-rapman-3dprinting

• Print the 2 parts
• Move the print head into home position, lower the z stage a bit
• Disassemble the existing z switch holder
• Assemble the new one (you need one additional M3 screw)
• Find a good position for the new z switch holder
• Attach it temporarily with double sided sticky tape and test that the position is good by performing a home sequence (switch off your RapMan immediately if it fails!)
• Drill 2 holes into the z stage platform at that position
• Fix it (2 M4 screws with nuts and washers)
• Test it again