I have to use the headshell weights on my Stanton 520 SK's, or else they skip. It isn't a problem of tonearm or stability, or not being broken in, they're just crummy cartridges
if you're getting clicking and popping, it probably isn't from a messed up cable. Did you make sure the output levels on your mixer aren't too high? That could def cause some problems.
The washer mod is definitely a good one. It also really helps if you're one of those people who don't like the clicking sound at your fader ends. The credit card mod is alright. What kind of mixer are you modding?