How can a Nightly Compose be installed?

[Petrus de Calguarium]

I downloaded last night's Nightly Compose of Rawhide, 
burnt it to a disk (I tried it in qemu-kvm and it 
works) and booted it.

After quite a long time, and long pauses between 
reading the disk and stopping, finally a mouse pointer 
appears on a black background, but even after waiting 
30 minutes, nothing else happens.

I switched to a different virtual terminal and typed 
liveinst and after a long time a line appears that the 
font is being loaded, but then nothing.

I rebooted the disk and this time tried liveinst -C (I 
think it is), to get the text-based version. This does 
indeed run, but when I am asked how I want to 
partition, it only offers to wipe my whole drive, 
replace an existing linux installation that it is, 
however, unable to locate, and some other unacceptable 
option, but does not allow me to select a partition 
that already exists that I want to use.

I also tried using liveinst as a boot parameter, with 
the same results as above.

The graphical liveinst might be the better option, 
assuming that it allows me to choose the partition I 
want, but X will not start.

How can I get X to start with a nightly compose and 
how can I install the live disk to the partition of my 
choice without destroying the other partitions (as I 
always do when I reinstall my system)?