Actually, instead of fish paper you could fold in something conductive, a strip of copper braid sandwiched in the fold would significantly reduce the load on the nickel alone. Because its sandwiched you probably don’t even need to solder it, tack it on in spots with the spot weld on the edges and you have a solid inbetween connection. But even without, 5 strips at 120A is probably fine. Continuously non-stop it might get hot, but for short periods of time it should be just fine.