I was going to suggest 2 footers, which you already did, but a subreport is a different beast. I try to stay away from formatting on a page level for subreports, as I don't 'know' that they 'know' what page they are on. They don't have page headers and footers, and can span multiple pages, and can have multiple groups on 1 page, since they may displayed several times on 1 page.
I would try to move the logic out of the subreport and into the main report. Shared variables will transfer values.
It's a thought, hope it helps.