If you are using mach3 why not use the built in touch sensor system. That can be used with some plugins/screen sets on mach3? Like this - http://www.cnczone.com/forums/mach_wizards_macros_addons/56079-xyz_probe_modification.html
A very valid point Nick, you can use whichever system suits you best. As I said in my introduction "The method used for tool position setting is a matter of personal choice but this is what I do". Tweakie.
I have a printed mount for the exact same laser. I've been using it on a tool change design, for calibration. Looking forward to part II.