Im currently in the process of adding a 6th string to my 5 string squier jazz like this:
Squier Deluxe Jazz Active 6-string? Yep! (pics)
It does already have pretty wide spacing though, so its going to be a narrow 6er.
what is the spacing like already on your Geddy Lee? Does it have open pole or whole piece pickups? if its open pole, you might have to replace them.
IMO I really like the idea of a narrow Jazz, hence why Im doing it myself to a £200 bass, not to something more expensive

still.... The only trouble I have had is through my own carelessness where I have chipped the paint on the head a bit...
I say go for it
