Datum retaining vise stop - video

[Mook]

Double-end feature is useful enough, not convinced about retaining position after swiveling the arm.
Without dowels insuring perpendicularity of mount with vise bed or that of jaw. . . .

I'd leave end of mounting bar full diameter, relieving the inner face somewhat, and longer to protrude from both ends.

In hindsight I would also leave the mounting bar at a larger diameter for better location.

If the mounting bar is set parallel with the bed the arm is then parallel with the Z axis & retains the X axis position.
I now use a die spring to hold the arm with no need to tighten it anymore see images.