My guitar's action is just a smidge too high. On the lower frets, it plays fine. But up past around 12 or so it's just a little bit too high to comfortably solo on. I've adjusted the truss rod and the bridge can't be lowered any more without buzz. So should I take the neck off and place a small shim in the pocket? If there's another way to correct it, please let me know. Just got a pack of strings and was wondering if I could fix this during a set up.
Shim is needed only when you have high action and cannot lower the bridge any further. In this case your problem is the fretbuzz point. I don't see a shim would help you at all. Check your setup again. Remember that the neck should only gives a slight bit of relief. Too much relief and you will end up with high action toward the higher frets.
^ what he said.....also remember if we are talking about electric guitars it's normal for a small amount of buzz to be heard without an amp, but as long as no buzz can be heard through the amp you are good.