I have a similar issue with a live image I downloaded in January 2017 and installed to USB with uneetbootin and a slackware 64 current installation on a laptop.
I've partitioned the hdd so as to have efi on sda1, / on sda2, other partitions for /var, /usr, etc
I worked out that to try in the setup2hd utility to target a partition with /usr automatically starts the install stage.
Same again when targeting /var to a partion.
As a work around I made the / partition bigger so as to incorporate /usr
The partition that was meant for /usr is now much smaller and targets /usr/local (that did not kickoff the install stage)
Then targeted the last remaining partition as /var which kicked off the install stage.
There were some error that appeared which did not stop the installation:
"rsync: write failed on "setup2hd/usr/share/locale/(can't see what's in here from the pic taken)/LC/MESSAGES/partitionmanager.mo": No space left on device (28)"
the utility then asked kept on gong until it reached 100% which were followed by other questions to make the system bootable and it did find /dev/sda1.
On reboot, it loaded the original 14.2 lilo.conf and kernels prior to this upgrade but nothing towards the 64 current install.
I may have to go back to try and burn the dvd to disc instead of a usb and see how this goes.
Interestingly now that I'm posting this from the live usb, i cannot see anything on the / target partition /dev/sda2
root@darkstar:/# mount
none on / type tmpfs (rw)
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
tmpfs on /dev/shm type tmpfs (rw)
tmpfs on /tmp type tmpfs (rw,nodev,nosuid,mode=1777)
tmpfs on /var/tmp type tmpfs (rw,nodev,nosuid,mode=1777)
gvfsd-fuse on /home/live/.gvfs type fuse.gvfsd-fuse (rw,nosuid,nodev,user=live)
/dev/sda2 on /mnt/tmp type ext4 (rw)
root@darkstar:/# ls -alh /mnt/tmp/
total 20K
drwxr-xr-x 3 root root 4.0K Mar 4 15:14 .
drwxr-xr-x 1 root root 100 Mar 4 08:40 ..
drwx------ 2 root root 16K Mar 4 15:14 lost+found
root@darkstar:/#
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