Hi David,
I would not wait for possible changes/fixes.
In my experience flexible heights in a sub-report in the sub-report's non-detail bands invariably fails to properly communicate height requirements to the main report. Equally placing sub-reports in the footer band should not be too tall. I don't recommend using the summary band in the main report for sub-reports.
Workaround could be to place the summary sub-report in the detail but only show it for the last row. Of course showing it once and retrieving it many times is not a good idea....
Alternatively create a new composite report with the existing main-report as a sub-report followed by the offending summary sub-report, if that makes sense.
Lars