Great to see you playing around with this method. I ended up using the wire version with a microscope to straighten the master rail, i.e. 1D. The original version you are copying works fine but unless you have access to a precision scanning laser it can't be used for 2D leveling (bringing two rails into plane), the optics in a normal line leveling laser are insufficient as the line is not straight enough.

Also we would need a different type of sensor to pick up a scanning laser.

What are you planning to use it for?