I say go with 6AWG so you can have 48A @ 240v which is pretty damn close to 70A @205v. Foot long jumping sparks and all. First I have heard of that happening, when I was younger we had a paddling pool, it was about 50ft long and you could dive in it, when I got older it shrunk to 5ft. But if you don’t know what you are doing maybe you can call a friend who does, as long as you shut the panel down and don’t install the breaker until you double check everything nothing will happen. In fact you could run the wire to the panel, but the breaker, fit the Wall connector and get someone to hook it up. Most of the cost is for wrestling with the wires.