ShipDTL and OrderREL Table linking woes

Okay, so my goal is to display TotalValue/TotalInvoiced/Difference (open value)

in a report.

Problem, when I link OrderRel and ShipDTL (for Shipdtl.invoiced, ourshipped quantity's), thing get very skewed when orders do not have pack slips.  I tried a left outer join, which seemed to help, but my totals aren't matching up.

Thanks a lot advance.