TBH I've never played with soft raid (or any raid really) I don't have any idea about it... But let me know how you go and I might be able to help out if you have any issues. It would be good to know as TBH I'm surprised it isn't something we get asked more often...

FWIW the next release; v14.0 (based on Jessie) is in heavy development and hopefully shouldn't be too far away. Many are basically done already, but the fileserver isn't one of them...