if you want a 1% or less voltage drop the calculator says you need a 2/0 cable and you can get away with a 6 ga at a 5% voltage drop over 70 feet. 10ga is serioulsy undersized for a 120 watt set up with a 70 foot run. myself I would probably try go as large as I could but there are a couple things I look at, cost and storage. so is the cost worth the extra benifit and can I store that extra cable easy. if I was doing it I would probably replace it with a 2ga if you can wire that into your controler, but some controlers will only accept a max size if thats the case just go to that and call it a day, or leave it and get what you get.
