Error while validating RDL content

I am building a report in NAV 2009 SP1 for classic client use only.
I am attempting to clone a report using posted tables from an unposted tables version.
I used to be able to just change the tables and fix any hard coded table names.
With the datasetFieldName it is no longer practical since it does not change when you change the source expression.

Is cloning a report with different table names no longer possible with this great advance or is there a way to regenerate the datasetfieldnames - or can I just drop them?
I dropped the report to text and it looks like I can't just do a mass replace.