No, you are not missing anything! We look after a number of sites that use Backup Exec 12.5 and we have had to create a script to stop and start the services before the backup runs to pickup the correct drive! It was sooooo much easier with tapes!!
Are you using each removable disk as a different drive letter? How do you catalogue the hard drives on a different server (in the event of a fire for example where a server is destroyed, the catalogue option for hard drives doesn't seem to be there!). Do you have problems with the IMG folders not overwriting?
shirmal