I was playing a friend's bass today because mine's in pieces in my living room, and noticed some serious bow in the neck. looked to see if i had the tools necessary to tweak the truss rod a bit, and discovered there's no nut. just a threaded rod sticking out of the cavity a little bit. it's a Yamaha PJ 4 string. body's very light (in weight), and dark in colour. mahogany? couldn't find any model number or anything on it. felt nice except for the bow in the neck... is the nut a standard size? anyone know what size a yamaha might use? where to get a proper nut? i'd like to help him out by setting up his bass, but can't do anything without a trussrod nut... Any ideas?