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The simple thing to do is ask google. Unless you are trying to game the system (as many do) they wont ban you, I think they'll just link your accounts and prevent you being able to double serve accidentally.
I would love to have a second account just to run the CPM campaign run to its full potential. I am not trying to double serve just get the most out of it.
If they know you have 2 accounts they will link them and they will act like 1 account, unable to double serve.