.2 in 30mm pure nickel is what i use for 99% of what i do. See the link below for some good eskate use case ratings. 30mm is the width i use to bridge but the dimension that carries the current is the length that spans the cells so if flat p groups it will be something near 50-60mm of .2 nickel putting you calmly in the 90a green column or 180a ish for maximum which seems about right in my opinion to keep your pack running cool.
Wire and nickel current ratings
I get my nickel from amazon and have had good luck but remember to rust test every order - i had the same seller i used a few times before send me nickel plated steel. They fixed it but it was a pain to wait for the second shipment.