Hello!
I did exactly as you described, but When my format came to 100%, my Amiga froze, and I could only move the mouse. I could not do anything. I waited several minutes, but nothing happened. When I rebooted the computer, the partition was still uninitialized.
I tried to make a partition on 16,7GB.
Now I have formatted the partition with FFS, and everything works well.
/Jörgen