The Stab fuel is used long before the Centre Wing Tank fuel is depleted. It's a few years since I flew a 744 with a stab tank (freighters don't have them), but from memory, the stab fuel transfers to the CWT during the climb.
If the stab fuel fails to transfer then the CWT pumps must be switched off and fuel burnt (not dumped) from the other wing tanks until down to MLW. Failure to do this will result in the CofG exceeding the aft limit.
Airclues