scratch the copper!
Well if I were asked, I would say you should run 2 hots a neutral and a ground, as opposed to a single 120v feeder. Is it possible to just put a seperate service and meter on shop? If not, than you could run an aluminum 2ot urd./with a #4ground wire (also aluminum). This will allow for 100amps easily. And is fairly inexpensive. And yes you are correct you should also have a ground rod for out building service. Copper is just not necessary in this case. Good luck, and welcome!
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