Probably right. Just invested in a set of graph tech saddles for the Les Paul, may just go for saddles and nut for the SG. If that doesn't help, a mate has offered me a set of Sperzels he has lying around, although I may be reluctant to start drilling into the headstock if that becomes necessary. The guitar is only about 8 years old, but on examination there appear to be no issues with the fretboard or with cracks in the neck, thankfully. An online check reveals that this can be a problem with the SG, with most proposed solutions being along the lines you've suggested. So cheers again, mate :-)