I wanted to combine the original arm with the current one so that the sensor is held completely by its washers and nuts. The current design has only a half circle which I find does not hold the sensor that well.UPDATE 7/8/2015:There are four versions. Version I Version 1 requires supports to print and should be printed so that the sensor holder portion of the part is on top. This prevents the supports from damaging the JHead portion of the arm. It does not have any holes for screws.Version 2Version 2 is designed a little thicker and has material to fill in the front of the arm so that when printed flat, no support is needed. It may also make the arm a little stronger. Longer screws are required. It does not have any holes for screws.Version 3:Same as version 2 except that it has the holes.  On my setup using the V1.0.2. back plate, they matched perfectly.Version 4:Same as version 3 with holes but I squared the area where the sensor mounts to provide more "meat/strength".I am still planning on making a version where the arm will include an area for mounting a hot end fan. Think of an all in one arm :-)