My best vise has loose jaws, which are too hard for some work, and let heavy items slip.

I'm thinking of making
(1) soft jaws (aluminum, maybe copper)
(2) step jaws (so I can hold something and hammer down on it)
(3) curved-face jaws (to hold pipe)
(4) milled jaws (to hold).
(5) V-block jaws (a V that stays put on the fixed jaw, but leave the
moving jaw flat)

So, are there any tricks? The jaws are held by 1/4-20 cheesehead Phillips screws;
I'm likely to go with flathead socket screws for the refit, 'cuz an allen wrench fits
better than a shorty Phillips screwdriver, and a flathead counterbore can force
the jaws down into their seat.

If there's too much clearance, can I bend an ell in shim stock and put that
between the body and the jaws (seems like that SHOULD work)?

Is there an aftermarket for vise jaw inserts I can shop in?