I recently purchased a used Washburn AB-25 Acoustic 5-String Bass in what appears to be like-new condition. When I first bought it, it played fine and the neck relief seemed just right, but it had bronze acoustic strings. I like a smoother feel, so I first switched to GHS Brite flats (the unamplified volume isn't crucial to me), then to Labella nylon tapewounds (the version sold by Carvin at a bargain price, which sound great, both amplified and acoustically). My problem is that I can't get quite enough neck relief with the new strings (the LaBella's are not especially light guage, running .060, .078, .097, .115, .131, and should have enough tension to produce relief). I have loosened the truss rod bit by bit until the rod's hex nut no longer provides much resistance to turning (in other words, it seems pretty loose). Still, the relief didn't increase. My target is to be able to cleanly slip a Fender thin pick between the strings and the 8th fret when the string is held down at the 1st and 15th frets. Any suggestions?