Regarding low string buzz and rattle;
I have found with both my Series basses, that the angle between the tailpiece and nut is just shy of providing strong downforce on the saddle, and that's where my rattles come from.
My solution has been to put a bend, gently, but sharply, on the ball end, such that the string exits the anchor slot as parallel as one can get toward the bridge; on some softer strings I have also done the following: taken a wee piece of core, or a short length of guitar string, wound .036 or so, and twist-tied the bit of string around the low string, using wee pliers, anchoring the segment of string between the bridge and tailpiece to the saddle adjuster screw, to provide just enough downward pressure to keep it solid on the saddle.