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I'm too afraid to risk losing the sites for a few months on established domains nowadays with Google. It's a shame because I have been able to pickup shorter domain names over the years.
It sounds like you want to have duplicate sites? If it is different content then your not going to rank very well anyways after they figure out all the content has changed.
You need to contact ALL link aprtners and get them to cahnge links, you need to get your arse out of the sandbox.
It could take 6 weeks, or 12 months, its basically a new site as far as google is concerned.
IMHO forget the 301, do a meta refresh first for 6 weeks. Google will then transfer the rankings and pr to the new site, THEN do a 301.
Having tanked two sites with a 301, then tried the refresh THEN 301 method for another it works a hell of a lot better.
hope you understand