This is a known issue with portals, particularly if they are set to slide up.
Do you have just one portal on your layout?
If so, you can set up a list view layout based on the portal's table with fields from the parent table included in the header, grand summary and/or footer layout parts.
The invoices starter solutions that come with FIleMaker 11 and 12 use this method for printing an invoice.
What you describe should not be an issue for the solution that I am describing.