One thing I have to remember.
The ASPNET user no longer exists and will not be used by the web application when accessing SQL Server. You will get an error - Login failed for user 'NT AUTHORITY\NETWORK SERVICE'. This user does not seem to exist, though. It appears to be hidden but does exist inside the IIS_WPG group. If you add this group as your SQL Server Login and give it the access permissions previously enjoyed by ASPNET then it should work.