RN104 - Stuck "Booting..." after automatic 6.4.0 upgrade.

I have a brand new RN102 and powered it on with new 1TB drives, all looked good but once the 6.4.0 upgrade installed yesterday it never came back online after the reboot.  The message said Not to power the unit off but to call Netgear Tech support so that's what I did. They had me try the factory reset, and USB recovery tool several times with no success. RAIDar could never see the unit either - it was getting late so never got any further last night.  Called support again tonight and got escalated to next level but after trying various things the guy determined the chassis was bricked and the unit needed to be replaced.  Didn't want to give up and pay the shipping back to N3w3gg so gave it one last try.  The instructions say you need a USB flash drive less than 8GB and I only had one 2GB drive and several 32GB drives. 2GB didn't work, tried partitioning the 32GB USB 2 to a 4GB partition but that didn't work, tried the same on a 32GB USB 3 drive (also partitioned to 4GB) - tried front ports, back ports, no success. Finally last ditch effort took my 32GB SanDisk because that one has an LED (that showed activity when trying it with the 4GB partition but even though I left it 20 min nothing happened).  I dumped the 4GB partition, reformatted the full 32GB as FAT32 and installed the 6.4.0 firmware using the usbrecovery.exe tool and voila - the system restored the firmware and powered down - only took a couple of minutes. Wanted to post this so others with the same issue don't give up to easily.  Try several different flash drives till you find one that works (seems like the 8GB ceiling is non-issue).  On the RN102, I had to hold the backup button while powering up or it would never start the power and backup lights flashing if I tried to push it after I powered on.  Hope this might help someone else.