Wires are like resistors in an electric circuit. One you know the maximum number of amps, you can choose appropriate wire gauge. So if you know the maximum number of amps that will go in at at time given your converter size, (mine is WFCO 35 amp) and max current draw out, you can determine wire gauge by knowing the distance the cable must run. Longer runs require a heavier gauge cable to accommodate the current without overheating than shorter runs. The resistance is a factor of length and gauge of conductor. This allows you to use lighter gauge cables on very short runs, like jumpers. I know this does not answer your question specifically, but it will help you understand why you need a certain minimum cable thickness, depending on where it is in circuit. Here is a good link to calculate the gauge you require.
FYI, I used a Camco 24" 2-gauge cable on my 2 golf cart batt setup, all been good.