I can say that with F19b RC4 you can install (and re-install over it) to:
* sda1: swap
* sda2: /boot
* The rest of sda was left unpartitioned.
* sdb1, sdc1, sdd1, sde1, sdf1 as a md raid5 software raid.
You need to use Custom Partitioning for that.
First create the /boot and swap partitions. Restrict them to the disk you want
them to be (there is a button for that, the one with the 'tools' icons).
Then create a / partition, make if smaller at first. Then restrict it to the
disks you want it to make the raid5. Then switch it to raid and select raid5 and
change the size back to the maximum and 'update settings'.
I still do not recommend to have the / partition on a raid5 device, but it can be done.