From a DMM Advisory sent by the USPS today:
An advance copy of the Federal Register notice changing the address standards for flat-size mail is now available on Postal Explorer. The new standards are effective on March 29, 2009, and require mailers to place the delivery address in the top half of all Periodicals, Standard Mail, Bound Printed Matter, Media Mail, and Library Mail flat-size pieces mailed at automation, presorted, or carrier route prices. Additional formatting standards apply to all commercial flats.
The advance notice can be accessed here:
These new addressing standards are one of the steps necessary in preparation for the FSS Flats Sequencing System equipment to be rolled out. Mailers need to be aware of these changes so that they can be implemented into flats design in the future.