You can (if you have one) boot off a DLT8000 which you should be able to backup your ignite image to it. It has a native capacity of 40Gb and depending on compression get the 73Gb your after. You not going to know unless you test it.
It depends on the tape that you use. If you use DDS tape drive, the maximum is 40G(DDS4). If you use DLT tape drive, the capacity will be up to 200G or more
//* What is the maximum amount of data that a make_recovery tape can hold?
A make_recovery tape can hold as much data as will fit on the tape. If make_recovery is run in the foreground it will prompt for more tapes if they are necessary. NOTE: individual files may not exceed 2GB due to a limitation in the pax command. *//
This should not be a problem as it can spam multiple tapes. make sure that you label them properly.