Pie Charting a Sheet Summary Report

I have added a RAG status to all my projects in the Sheet Summary view. I can pull a report showing the projects and their RAG status fine.

When I then try to pie chart the RAG status onto a dashboard this is not possible as the RAG status is not a number.

So I added a number field and populated it with '1' so that I can add the RAG status and a number to a pie chart, but then the pie chart returns a segment for each row in the report - it does not aggregate them. So for each Green status, there is a pie segment and so on.

So I try to aggregate my Sheet Summary using a sheet - but you cannot access Summary items in a sheet. So as far as I can tell I cannot chart out Sheet Summary items.

Unless I'm missing the obivious, Sheet summary is good for reporting, terrible for dashboards.