Windows 7 (and Vista) don't use a GINA, they use credential providers, so yes it's possible (and supported) but does not work the same as XP and before.
EEPC only supports the Windows credential provider, we don't support third party ones as there's no longer any "chaining" capability.
Here's what I did for Window 7 for SSO.
Created a new machine group called windows 7.
Properties, General section
Checked Require logon to Endpoint Encryption
Checked Attemp automatic Windows logon
Checked Automatically logon as pre-boot user
Checked Endpoint Encryption logon component always active
Checked Set Endpoint Encryption password to Windows password
Checked Must match Windows user name
Checked Do not display previous user name at logon
Checked Disable checking for AutoBoot
Checked Do not lock workstation if no user is authenicated
Checked Do not lock workstation if user is disabled
Of course add your own settings,
Once you are done create a new install set. Then test it on a Windows 7 workstation.
Hope this helps