[Sardy]

Almost done. Just a little plastic putty to fill small gaps and some paint for the finishing touch.
To do some testing, i drilled a small hole in the back casing to fit the wires of the new battery through. Everything was working fine, so i jigsawed a piece of plastic out of the casing. Taped the new battery in place and the had to think of some sort of cover. I made one out of plastic but decided to make a new one from a piece of scrap metal, because the plastc cover added a little too much height to the construction. The metal cover feels a lot more solid too. The cover needed some paint and after some experimenting i'm quite pleased with the result.
Hopefully the battery indicator and its circuitry will adapt to the new battery after some charging cycles. Today it switched the DR off 3 times because of an "empty" battery. After a reset i'm stll reading without a recharge! I'm trying to really drain the battery before recharging it.
I'll add some pictures of my DR "surgery".
On the pictures: the old battery (top) and the new one (and the on/off switch i already added earlier, the additional wiring you can see top right leads to the new usb connector). The jigsawed hole. The new battery rises about 2 mm above the casing. The painted metal cover and the final fit.