Backup Z5 32.0.A.5.19 firmware

I've just bought a Z5 Dual (E6633) that has 32.0.A.5.19 firmware. I want to make a backup of the firmware so that I can return to the original in the future. I've tried to make an ftf file using the Sony PC Companion and flashtool. When the software update has finished downloading there are no files named FILE in the blob_fs directory. Is it possible to make a backup of the original firmware? I haven't been able to find 32.0.A.5.19 ftf files to download either. Is there any way to get the 32.0.A.5.19 for the Z5 Dual E6633?

Thanks.

from xda-developers http://ift.tt/1N5PUcW
via IFTTT