Just stumbled upon this project and WOW!
Completely stock ancient Dell Optiplex 755 was on my workbench so I attached two drives and now I have FRANKENSYN!
Control panel shows:
Model name DS3615xs
CPU Intel Core i3-4130 (actually is even older, a Core 2 Duo)
DSM 6.2.2-24922 Update 4
Happily running in RAID-1 with two 1TB drives, lots of little files copying to it at around 320 Mbps ... not bad!
This is AMAZING, thank you to everyone who had a hand in it!!!!!