I got real tired of constantly recentering and replacing soft jaws on my Saunders Machine Works hobby vise .
it’s awesome for plenty of things but I do a lot of coin/token prototyping and (in theory) a self centering vise would let me swap out coins of all sizes without re-zeroing.
Enter the Xin Dian self centering vise. A little ~$70 import that seems to be good enough. Only problem is there’s no way to hold onto it.
So I cut a fixture plate out of delrin. It fits the hole pattern on my SMW m6 Nomad bed.
The bolts underneath are fully countersunk sub-surface so they do not contact the bed. In theory this electrically isolates the vise to facilitate conductive probing 
The holes in the corners are used to bolt the plate to the bed and the 6 additional holes along the side are reamed 6mm to get some repeatability by way of the SMW locating pins 
Is it super rigid? No. Does it eat Z height? Absolutely.
Neither is a problem with my particular use case of very low profile, very low cutting force operations. Gotta appreciate the little wins 