you want your power and ground to be the same size.
in this particular situation you could probably get away with it since your power wire is overkill, but i still wouldn't just because it's only a couple bucks more to get the right size.
here's a picture of how it goes together with a stinger 1/0awg pro terminal. very simple and clean solution however i have decided to go with a circuit breaker.
i have 2 stinger 0awg pro ring terminals (like the one pictured) that i will include for $16. they are for my personal use but i have to make another order anyway so if you want them i can reorder.