Time Phase Material Requirements Report - "Modify Filter Tab to allow users to see negative balance results"

Has anyone modified a built in report’s “filter” tab to add additional criteria? (I think the filter tab is a BAQ) We have a request regarding the “Time Phased Material Requirements Report” where users only want to see items with a negative balance value displayed on the report. Before I attempt to copy the standard report and then add a filter inside the report itself to only return negative values. I thought it may be worth a shot if the filter criteria can be modified.