Jwglista,I use Scotch electrical tape.I start with pulling from the roll,then fold it at 1/4" lengths,or longer if desired.Keep folding until desired thickness is reached.I use that for spacing.Sometimes when things don't sound right,I put a couple of layers on the arm before mounting cartridge. If both aren't completely flat,it acts like a gasket filler material,and keeps vibration(rattle) down between arm,and cartridge body.Its cheap,you could keep changing thickness,and it works for me.Use extra care in tightening the screws.I don't think you need it very tight.I never had one break,but heard others have.