I wonder if it's possible without re-registering?
I'd guess that it can't be done within the same registration. I bumped into the name issue when changing from MaxFixit to FineTunedMac. I don't recall all of the specifics but I do remember that, once you have a name registered, it sticks.
I don't think that's unusual. When I wanted to change my user name at a financial site, it required a re-registration.
