I haven't put my hands on it yet - in the post tomorrow.
Seller says he took it to his local luthier who reports the truss rod is maxed out - some say it's just a matter of adding a couple of washers (though so far all I know is 5mm internal, no external measurement). One parts supplier suggested that Yamahas (well actually Ibanez) don't use single action trussrods. As far as I can tell this is.
Anybody know better? (I'm assuming that @AndyTravis does).
Photos to follow.
I have absolute faith in Gary's work - he set up my HB Tele - and though I'm no expert, guitarists who have tried it have made positive noises.