Elsie,
PPRuNe is always reliable in producing lots of, um, constructive criticism, but the FAA does produce permits for going overweight for long ferry flights and I would like to be cautious and know what the performance is likely to be.
I broached this in the test-pilot forum because I know that this is where the "envelope-pushers" are going to reside, by definition.
I do hope that you are not the first of many and that we can have one of those rare PPRuNe discussions that does not turn into a slanging match.