The purpose of this remix is to enable the spindle carriage to travel past the leadscrew coupler on the X axis. Doing this will provide an extra inch wide strip's worth of workable area running the length of the work surface.
Other things I've changed in addition to the notch:
-I enlarged the mounting holes for the linear rails by 1.66% (my experiences with the previous tolerances consistently led to breakage).
-I added 4 loops to the underside of the carriage. These loops are intended to accommodate a ziptie, the function of which is to keep the linear rails from falling into the work area in the event they were to vibrate downward. I understand this fear may just be paranoia on my part, so I've included STLs with and without these loops (V1=no loops V2=loops).
I highly recommend printing this piece in the orientation illustrated in the Cura screenshot. This way the printing striations are running perpendicular to the shafts for the linear bearings making them far less likely to split under the strain of installation.
If Printing V2
Once you've removed the support material and added all of the necessary components for the CNC, take an appropriately sized zip-tie and thread it through the 4 loops, then take a second identical zip-tie and zip it tight to the threaded tie, then cut off the excess on both ties.