A friend of mine has kind of a cool setup-he took angle iron, heated it up and put it in his post vise. He hammered down the piece that went over the curved back of one jaw, the other part is pointing down, on the inside of the jaw. Then he took and welded a piece of metal to it and ground it flat. Did one of those for both jaws so the welded on pieces meet smooth and flat (is this making any sense?). When he needs to straighten stuff out, he just sticks it in that vise and tightens it up. Best part is, the angle iron pieces over the jaws just lift off and you can make different kinds (lined with hard rubber, leather, whatever...). Just my inexperienced $.02. Hope you find something that works for you.
Jeremy