Okay, so I've usually only shimmed a neck if the action was too high...but after some reading here, it seems like it's pretty standard to shim to sides of the pocket too? To get tighter/better connection between body and neck. On a very well built strat, you should be able to take off all neck screws and lift the guitar by the neck without the body falling off. Correct? So: What are the best shimming materials to use?