I watched a friend install an old version of NetBSD on an i386
box.  Instead of using multi-volume tar's it seems they had just
taken a "file.tar.gz" and "split" it up, then put them on floppy.
There was a bash script (in .profile of root or something weird
like that) , when you typed a command it would prompt you for the
disks one by one and essentially do the following:

  ( foreach disk cat the disk ) | tar -xzf -

Seems simple enough to create and gives the programmer more room
for interactive instruction.

                              Tim N.