hi James,
may i make a suggestion on a redesign of the report so that you can avoid having a subreport and hence a 2nd stored proc? if the summary.jpg is the format that you're looking for, and the subreport is only making an aggregation of records that are on the main report, then you may wish to use a cross-tab object in place of the subreport. this way you're only running the query once and you don't have to worry about linking the subreport.
i'm assuming that the subreport stored proc is doing all of the aggregation correct? if that's the case then the data brought back to the subreport probably can't use a Saved Data filter as there would be no detailed records in the subreport to apply a changed date range to.
if that's not the case though, in order to have a subreport match a main report, then recreate identical parameters on the subreport, copy over the main report Saved Data filter to the subreport, and then link the newly created subreport parameters to the main report parameters by clicking on the subreport and choosing to Change Sub-report Links and then link the main and subreport parameters directly to each other.
-jamie