Where can I find information on migrating from Business Objects 5 to XI R2?

We want to migrate several Business Objects implementations - some of which are Business Objects 5 and some Business Objects 6 to consolidate them into a XI R2 environment.

I have the document that describes migration from 6.x to XI R2 but what is the process for migrating from Business Objects 5. Do I need to migrate from 5 to 6 and then follow the 6.x to XI R2 migration?

Any pointers to additional hints and tips on migration or how to estimate how much effort is involved would also be welcome.

Thanks in advance for your help.