Soldato
Yeah, doesn't look too hard, but a little fiddly, I probably wouldn't risk it myself.
Thought I would struggle with it being so small, but it's quite an impressive device.
I'd go Amazon.de if you can. Longer warranty (two years as opposed to one with Amazon.fr) and in my experience better support.
Does under volting help with battery conservation?
Just got 5.1.1 ota ... Finally