TandemVids works with Vegas 8.0 and DVD Architect 4.5 but hasn't been fully tested. I have at least one customer using Vegas 8 and don't know of any issues.
It should work but if there are any issues, I can't promise I'll rectify them as the number of users is too small. I don't own Vegas 8 and need to reference an expired trial edition when I build TandemVids. This means the references work for Vegas 8 or higher but I can't test Vegas 8 properly without buying a license and that's not possible through the correct Sony channels.
You can download the freeware version of TandemVids and fully test your scenario using Vegas 8 before committing to a license.