This is odd. I suspect it's a bridge adjustment. I adjusted the truss rod for the final time, and the D and G strings are vibrating the frets. But not the E or A. I suspect this means the saddles need to come up a bit on the high side, and could probably be dropped a bit on the low side. Where do I find the allen key? What size is it? Also, is there a way to get the action down high up on the neck? I've heard shimming, but I don't know how or where to do it?