(For purposes of possibly helpful sidetrack conversation contribution...)Maybe newer ones were better? I never even heard of deburring the sides of them or peeling them. I just stuck them in and used the piece of tape on each side trick, and they worked fine.
Have you heard of burning the end and separating the two sides out?
The copperhead had poor performance imho due to the SOP of just one sided contact surface and with some clubs having rusty or old alligator clips, half the contact surface means twice the likelihood of "failure to launch" (haha, I just wanted to say that).
They worked OK for me when I burned the ends, split the layers and wrapped them around the clips... improving the contact maybe 10x.
YMMV