I was making a large kitchen knife for a client, when I realised that it wasn't going to fit in my knife vices to shape the handle. So I made a new holder that bolts onto the existing bracket just for this one. It is a monster - 75 x 25 x 350mm. Enough for the biggest of blades. It needed three screws to squeeze the blade tight.
A nice feature of the Knife Vice Mark II design is you can have different sized clamps that fits different blade. Easy to swap in and out as required.