5A cuz you have 2x50 watt that on the back suggest Imp of 2.78 each. 2x2.78 = 5.56A
30' may be stretching it, but with a programmable controller, you can up the bulk voltage and/or extend absorption time to compensate or fully charge when you have utility power.
some folks seem happy with flat orientation limitations, other have converters that only do 14.4v with no temp comp or 13.6v!
With a fixed install, the controller is close to the batt to limit voltage drop, portable is a compromise that is likely better than most converters, 100 watts is not much for 2x6v but you might not be a power hog!