these are goofy bad pics but instead of having to solder on wires for flex between the groups of four the method in these pics is just a bend of the copper that can go down the length of the cell a couple cm and then back up to the other group and leaves a lot of material to bend. with this method, if it were to last, you’d need no soldering except the start and end of the 12s chain. I don’t know how long until the copper would finally harden and break and never made these to test. couldn’t find any better pics! and you can see theres a “guard” going down the length of the cell were the copper bends
and was just going to use nitrile high heat rubber bands for compression which I think is maybe a safer method than even the nese now that I see how little foam is used in those.
for the copper it takes so long to oxidize and especially with the contact to the cell having slight friction I doubt it would have a problem not being plated and you can get bare sheet easily and cut and press it with 3dprints easily.
layers of thin stuff were shown to have less resistance with better conforming contact on the cells than thick non conforming stuff. so easy to work with the thin stuff
plating with tin is easy and theres also some other easier coating method I found that doesn’t add resistance but stops oxidation forget what it was, some dip. I have rolls of copper from years ago look as good as new though