After address validation, run the command above. This command marks records that have enough pieces in a route to qualify for High Density rates (or better). After running this command, show the marked records.replace all x with " "
SELECT LEFT(zip,5)+crrt as zip FROM (ALIAS()) GROUP BY 1 HAVING COUNT(LEFT(zip,5)+crrt)>=125 INTO CURSOR _zips READWRITE
INDEX ON zip TAG zip
REPLACE X WITH "X" FOR SEEK(LEFT(zip,5)+crrt,"_zips")
If there are enough pieces in your list that would qualify for these low rates, run DSF2 from Data Enhancement Services on this list. Doing this will add walk sequence data to your list, and then when you presort, you'll be able to qualify for the lowest rates possible.
Doing this will not only save your client a lot of money in postage, that money savings should put extra money in your pocket as you charge for a percentage of the savings.