I suggest running a post style relay instead of a standard automotive. It's much better for connecting larger diameter wire. I run this one and was super easy to connect my 6ga wire from my battery.
PAC PAC-80 80-Amp Relay Battery Isolator https://www.amazon.com/dp/B001EAWS6O/ref=cm_sw_r_cp_apa_nXQyAbS4HJ304
PAC PAC-80 80-Amp Relay Battery Isolator https://www.amazon.com/dp/B001EAWS6O/ref=cm_sw_r_cp_apa_nXQyAbS4HJ304