Advice needed for exposing Astia and Provia

[Marizu]

I don't shoot much slide and the portraits that I occasionally shoot are usually lit with me controlling the dynamic range so incident metering works fine.
I'm making a set of photographs with a large dynamic range which won't fit into the slide but I want to ensure that I capture the aspects that I feel are important.
I believe that Astia has a dynamic range of 6 stops and Provia has a dynamic range of 5.
If I spot meter the brightest highlight that I wish to retain, what zone would I place that on for these emulsions to avoid blowing them out? (assuming meter and shutter are callibrated ok)
For example, if I meter a highlight as f22 at 1/125 second (zone 5) would I put that into zone 8 for Astia (+3 f22 at 15s) and zone 7.5 for Provia or do they have a bias up or down.
Or am I thinking about this all wrong?

I am planning on scanning these on an Epson V700.

Thanks in advance,
Marizu

[Joanna Carter]

I reckon on splitting the range of Astia 3 stops each side, so highlights in zone 8. Don't forget - expose for the highlights and hope that the shadows work