"I believe the official DA suggestion is to use hanging folders with ONE manilla file folder per hanging folder."
The recommendation is to ditch hanging folders, if you can. If you can't because the files will sit too low in your drawer without them, or you don't have enough files to lean against each other to hold them up, then use Hanging folders. The reason for one file per hanging is that many people overstuff hanging folders and have some files "prairie dogging" out of the drawer. So just don't overstuff the hanging files if you want or need to use them.