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Sadly there really isn't one. I know it doesn't help but the 301 shouldn't have been done in the first place. Changing URL's and doing 301's always impact on rankings in a big way. You will be best to 301 the new domain back to the old one and try to stay away from doing it. Also keep in mind every time you do a 301 you will only get 70-80% of the benefit of the links going to that domain.