I recently bought a Shuker Uberhorn at the Gardiner Houlgate auction. Lovely instrument, 5 string fretless, although it's 35" scale but I can live with that. However the action is stupidly high, because the neck is bowed. A 4mm allen key is too small, so I contacted Jon to ask his advice. He said he used to use ABM truss rods with 5mm adjuster - I couldn't get a 5mm allen key in without cutting it down, so I got one off Ebay and cut it down. I could get it to the end of the truss rod but it woul