This question was asked, but the answer is not practical as the subpanel is only for 20 amp 220 VAC So, quadruplex cable is overkill. What about something like marine cable? Or a 10-3 with ground (black-red-white & bare copper ground). or even a 10-4, in a weather & UV resistant jacket?
Like the temporary construction cables... Anything like that for low current (20A) overhead runs? It's all about cable that will survive the weather for many years. Perhaps they don't make something like that anymore?