I have a Zon Sonus 4 string bass that doesn't have a trussrod. Its neck condition's gone bad lately and I get buzz from around 12th fret and higher. I can't have it fret dressed by myself because I can't find a way to simulate the neck when it's strung up, and I think it'd be a smarter way to make it have a trussrod. So, does anybody know that if Zon guitars install a trussrod to a non-trussrod bass they made? I believe it'd be the best to commission this sort of work to the own manufacturer of the instrument, so I'm not considering taking this to any luthier around and do it. I wrote an email to Zon guitars and I haven't received an answer for more than 2 weeks. So you guys help me please.