YOY Bar or line chart with contributions made prior to the fiscal year showing in one bucket

Hi,

I would like to create a line chart (or column chart) showing total contributions by fiscal month. The x-axis will show fiscal month with a break on campaign fiscal year.  I plan to show 3 fiscal years for comparison. Our FY is Sept to Aug.

For any contributions that were made prior to the start of the fiscal year, I would like them to be grouped into a "month" called "Pre-FY-Start".   

I've been struggling with two things: 1) How to group the pre-FY start contributions and 2) How to display by fiscal month, since there appears to be no equivalent to the "Calendar Month Sort" field for fiscal periods.  

Has anyone had success reporting by month with fiscal year?

Thanks