Need suggestion in migrating the model

[madhancog]

Hi Gurus,
   I am working on cognos migration project.I need to migrate my impromptu Catalog to Cognos FM model and create the reports.
I had one Catalog and it contains 80 tables and all joins are in outer join method,now i need to migate the same to Cognos 8 model and i did the same,I know that having outer join makes all the problems in reports i performance,can any one just suggest me to make my model optimized.
What all the points i need to note from Cognos 7 catalog and how can i make it optimized pls help me out.

Thanks in advance,
K.M