CAJUN ACCORDION DISCUSSION GROUP
I have found that #8 bare copper ground wire works best. Seems to be plenty stiff enough. But, you can't mash the end where the screws go too thin or you create a weak point.
This has happened to me 3 times. The most recent occurrence, the wire broke in half right at the screw hole. This is obviously a point of weakness. On the advice of Dana, I fixed it myself with some super strong West Systems epoxy. I played one gig on it so far and it has held up.