I have wondered if a decent woodworking vice could be mounted onto the SS system, and have not yet come across one on any forum or youtube. So, I finally accepted the challenge and built a Moxon vice which drops into the 1 1/4 inch casting recesses at either end of my Mark V 510.
The jaws were made from 8/4 Sepele and are 28" wide. The screws are 16" apart which accomodates up to a 14" board between the screws.
I used the Rob Cosman version of the WoodCraft twin screw kit, which features springs for quick jaw retraction, pin handles on the wagon wheel, and oil soaked copper collars to reduce friction and catching.
I modified the tops of each jaw with my Domino jointer to make peg holes. Using dominos pegs, I can grip a board horizontally up to 4" wide with enough holding force to hand plane.
What is unique about this Moxon vice is the working height is easily adjustable using the twist knob on the SS casting. I can lower the vice for hand planing and then easily raise the vice for end grain work such as dovetails or jointery. Or, I can adjust the height simply to gain ergonomic advantage and spare my lower back

I purchased two extension table replacement tubes from Shopsmith for about $29 each. The Rob Cosman hardware was $188 shipped to my door. There are other Moxon hardware kits on Amazon for as low as $44. So the overall price of my Moxon verrsion was about $250, but I chose the high end hardware. With the affordable hardware, you could get the same functionality for about $100.
This vice does not replace a workbench, but it does extend the versatility of the SS system for common woodworking tasks. I can effortlessly replace the extension table with a non-marring woodworking vice and adjust the working height to my needs. One downside is that It does not accommodate long boards between the screws, but will grip them outside of the screws.
A bench vice should transfer the force of mallet blows (during chiseling) to the legs (and thus the floor). When this vice is lowered all the way so that the stationary jaw rests directly on the SS casting, downward forces are absorbed by the SS frame and thus transfered to the floor.
I did not video the build, but if you are interested in how I made it, reply to this thread. I have a few key photos and can describe the important steps and what I learned from this build.
Hope you find this useful.
Thanks