Max Token Size

Hi

Presently, the token is overweight. My DC is Windows 2003 and prepare to remplace by Windows 2008 R2. (The functionnal level to domain and forest is presently Windows 2003 and all client Windows 7).

When all DC transfert for Windows 2008 R2 and raise functionnal level, it's necessary to deploy a GPO to all client? It's neccessary change registery key?

I search a link to explain a best practice to modify a token size?

Thanks