1. I have used copper, 'stainless steel' and other electrically conductive materials. With your skin and body being very high 'Ohms' resistance compared to other electrically conductive TENS materials. I see no reason to favor copper over other electrically conductive materials. You can measure your current flow in milliamps with all that I tested. Many people also use a foot bath with salt water. The salt ' or other minerals' will lower the conductivity of the water. I now use only TENS pads. With the "CS" port on Spooky2 a 10,000-ohm resistor in wired in series (in the same wired path) with a TENS connection wire.
2. I think TENS Pads would make better contact since they have a moist flexible surface, rather than a dry skin to hard, dry metal plate. I haven't tested it because I don't use contact except for the footbath method.
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