Upgrading Firmware on ReadyNAS Pro Business Edition

Hello everyone --

I intend to perform a firmware upgrade on my ReadyNAS Pro Business Edition. The unit has 6 x 2Tbyte disks installed, single volume is RAID-6, but hasn't expanded as the initial 1Tbyte disks were replaced with 2 Tbyte versions because the original volume wasn't X-RAID-2 formatted - I never thought we'd need this much space!

I'm planning to delete the existing volume and rebuild as X-RAID-2 so I can use the extra space, and future-proof the unit to a degree, and then restore the data by performing a reverse of the unit's nightly rsync backup to a remote NAS (QNAP - sorry!)

Whilst I'm about it, I'm also planning a Firmware upgrade and installing EnableRootSSH to give me more granular control over my data, specifically users/groups and permissions on our files (some of them have been written incorrectly over SMB as the 'admin' user ...)

My questions are these:

1. ReadyNAS Frontview's Home page tells me my firmware (unchanged from 2009) is RAIDiator 4.2.5; when I go to System -> Update -> Remote to see if there's an update available (in 4 years I would expect there to be), it reports there's an update version 4.2.20 (x86) available. To me this seems like a downgrade rather than an upgrade. Am I misreading the version numbers, or am I confused in some other way?

2. Am I correct in my plan for recreating my logical volume, or is there another non-destructive way of changing from (Flexraid?) RAID-6 to X-RAID-2 with dual redundancy?

3. Is the firmware upgrade destructive in any way? I'll back up my existing config, but does performing the upgrade lose any of my existing settings?

4. I understand the Support caveats that go with EnableRootSSH, but I'm OK with this.

Many thanks for any advice, in advance.

Mike