We're working on to enable the page sections for subreports. Actually what we plan to do is to allow the users to display several reports subsequently thus every report will use its own page sections that is what exactly you need to do.
It is not possible to set the number of rows to display on one page (as a grid control does), because the main purpose of the reporting tool is to generate reports that are ready for printing, and when printed they should appear on the paper in exactly the same way as they are displayed on the screen. This limits the report pages to physical pages, so the number of rows to fit on a page depends on the size of that page (its height) and size of the sections that occur on that page.
All the best,
the Telerik team