I use a 5" Tormach machinist vise with ground vise keys. I can move vise on and off table at will with vise keys using the pre aligned center keyway on the mill table. Very accurate system to align tools like 4th axis, vises and other fixtures with little effort. You can even put keyway stops in place to move vise or other fixture on and off and still locate it very close to same place each time.
oops reading your post a 6" kurt would overhang to much if you use the key slots it has. You would need a smaller vise or mod it like others do.