Two things come to mind here - one is the bass might benefit from a professional set up by a really good luthier who may have some tricks you don't know to adjust the action down further for you on that set neck . The other thing is as mentioned - some basses simply aren't going to be as adjustable s you 'd like - due mostly to design or manufacturing choices . More expensive basses tend to have that adjust - ability available more than less expensive instruments and while the Supro is not cheap - it certainly is not an expensive bass and may not have the quality standards necessary for the low action you want . I'd run your dilemma past a good repair guy and see what is possible and what it'll cost ... Kelly