> My project is in P4 but I'm thinking of including in an extensions
> file the P5 tags for manuscript documentation. Are there any
> particular pros or cons of which I should be aware?
I'm not sure what your work-flow is like, so there may be very good
reasons to stay with P4. But as far as the document instances
themselves are concerned, it is probably just about as easy to switch
them to P5 than write the P4 extension that would be needed.