This part uses an existing Microjig Grr-ipper and hardware to bolt on an additional bit of security.  The part can slide up and out of the way, or slide down and grab the back edge of the board.  If you keep the bolt loose, it can use gravity to slide down.  Just be careful because you'll only be relying on the front screw to hold the center support in place if doing that.

Printed in PLA+.  I used 4 walls and 25% infill, and it's plenty strong.  Maybe overkill, but I didn't want anything snapping off while in use. 

Print it with the little lip upwards, and some support under the center slot overhang.

Obviously, don’t make a safety device less safe.  Use at your own risk and print it strong.