From Boeing 'Cold Soak' publication, May 2004
Boeing will incorporate CSFF permissable area in production starting with line number 1538 in July 2004, as a standard feature
- Lines on wing upper surface
- Manual updates to support operations will include Airplane Flight Manual, Airplane Maintenance Manual, and Flight Crew Operations Manual
Retrofit will be available as per Boeing Service Bulletin 737-11-1125
If you ain't got it, ask about it. I don't know how far it has got with 'approval', but the tests have been done and it is ok - and we need it!