Mandatory Roaming Profiles w/ XP & Vista

Here is my scenario...

I have a Windows 2003/2008 AD domain (single forest, single domain) running
in Native W2k3 mode. The Windows 2008 DC is basically installed to allow us
to use the new GPMC for our Vista clients.

I have approx 50 new Vista clients that I have added to our district. Up to
now all clients were XP and all my student accounts used a single mandatory
roaming profile. This worked like a charm. Now that I have added Vista when
my students "roam" between XP and Vista machines I get a ton of profile
related errors on the Vista clients. The XP clients still work flawlessly. I
know that Vista cannot use XP profiles so my first question is:

How can I specify a single roaming profile path in the students' AD account
properties that both XP and Vista "like"?

Should I upload a user profile from Vista to replace the existing XP user
profile I have currently in place and have my students' use that? I am
assuming then when they try to log on to an XP client they would receive
profile errors on the XP clients.

I downloaded and reviewed the 'Managing Roaming User Data Deployment Guide"
from TechNet but (in my opinion) wasn't real specific on how to approach my
particular situation. It did detail how to use Folder Redirection to get
Vista to use some data from XP profiles but nothing about "mixing" the two
together.

Is there a "happy medium"? Do I have to move all of my student PCs to Vista
just to resolve the lack of interoperability (or downgrade my Vista clients
to XP)?

If there is anyone who can provide an approach I would greatly appreciated.

Thx
Joe