Export 4 digit Onebox mailboxes to 8 digit Onebox

[Kronehead]

I currently have 2 Onebox systems - System 1 is production VM running OB 3.0 and was built with 4 digit MBX's. System 2 is in testing and running OB 4.01 and was built with 8 digit MBX's. I need to migrate the users from system 1 to 2 complete with all messages, greetings etc. I understand I will have to upgrade the OB 3.0 system to OB 4.01 before I can use the archive application to generate my .cxa file for the import. How can I convert the 4 digit MBX's into 8 digit MBX's on the new system? Will the new system accept the .cxa file and if so will it create the MBX's with 0000 prefixing the existing 4 digit number? If that is the case, how can I renumber all the MBX's with the extra 4 digits that I want to use? I am hoping I won't have to manually renumber all the MBX's in OB Admin as there are about 1500 of them