Disk space for virtual server update

Trying to test upgrade on a lab server.

12.1.3.4 install fails

progress: 96/100
info: saving package installation order...
info: saving initial package database...
csyncd-12.1.3.4-0.0.2.i686
info: Found -- csyncd tries to configure rsync
info: Found -- [csync] section in etc/rsyncd.conf
info: finalizing image...
info: Adding user/group files to customization data...
info: Forwarding previous dhcp client lease file to disk xvda, location 1 (/mnt/tm_install/14610.T6gtxb/usr/lib/install/dhclient.leases).
info: pscript Copying dhclient.leases to DHCP lease directory /mnt/tm_install/14610.T6gtxb/var/lib/dhclient/
info: pscript Create the VADC fetch key marker to install ssh keys: /mnt/tm_install/14610.T6gtxb/.vadc_fetch_keys
info: pscript Create the user key retreival marker: /mnt/tm_install/14610.T6gtxb/.user_public_key_install
info: Applying UCS /var/tmp/IqRzc4wHBm.ucs to disk xvda, location 1 (/mnt/tm_install/14610.T6gtxb).
info: capture: status 256 returned by command: F5_INSTALL_MODE=install F5_INSTALL_SESSION_TYPE=install chroot /mnt/tm_install/14610.T6gtxb /usr/local/bin/im -force /var/local/ucs/config.ucs
info: >++++ result:
info: Extracting manifest: /var/local/ucs/config.ucs
info: /var: Not enough free space
info:   2407819264 bytes required
info:   959385600 bytes available
info: /var/local/ucs/config.ucs: Not enough free disk space to install!
info: Operation aborted.
info: >----
Terminal error: UCS application failed; unknown cause.
*** Live install end at 2018/04/25 10:07:06: failed (return code 255) ***

Looks simply that the disk partitions on the unused set are not big enough.

Feels like a bug, since it is simply being upgraded following documented procedure.

I'll try extending root.set.1 volume, but not sure if this is recreated when installing the ISO or not.

What is the right^W F5 way to get the volumes built the right size?