I have been using a pair of vise grips with a 3/8" rod welded to the side of the pliers. It interchanges with the standard fly clamp or base and can hold a 5 ounce canal special bucktail with a huge wire hook without movement and no fatigue. Beats the heck out of trying to force a humongus hook into a vise that was designed for fly tying.
Cheap and effective!
