I made myself a clamping device with 6 pieces of keystock welded to an iron ring.
That particular setup is great, but it must be properly indexed. If the interval between supports isn't identical to the chuck, you risk tilting a jaw sideways when it's tightened. Not a big deal if the chuck is fairly tight, but if it's quite sloppy--it can be. Even then, you'd improve the chuck, though. The real benefit of grinding the jaws this way is to improve jaw to material contact. Chucks that grip only at the rear are a real PITA, causing excessive chatter and making it difficult to keep parts round, as they oscillate in and out under the pressure of the cut as the material flexes between support points.
I was going to comment earlier about the suggestion that one jaw appeared to be all the trouble. While it's a long shot, it's possible the chuck has been through a crash, where the part exited the chuck by forcing one jaw out, which would surely lead to some kind of damage. The description of the chuck tends to support the idea. Before attempting any kind of repair, it might be a good idea to remove all the jaws and examine the slides to see if there's any substantial differences in them. Even though a chuck might be improved, it's possible that any given chuck has simply outlived its useful life and you won't get the benefits expected. Just a thought.