The bonus does not stack, but I would not oppose two "one box" weapons...or a two-box weapon to indicate a paired set if it suits the concept.  Keep in mind that this is a custom-build sort of weapon. It's a signature item for your character.  It should be a big deal.  ;D<br/><br/>Foci are (in brief) narrative permission for special effects. Custom-made magic items that allow a bonded wielder to perform actions not otherwise possible.  Or in your case, something that lets you punch ghosts and elementals<em>harder</em>.  :-)<br/><br/>On Permutations...go for it. Up to two, and note your Drawbacks.