The shell kit came with 2 small brass hinges and 8 brass screws to fix them on the lid and main body. The gaps to insert the hinge leaves in the main shell were nearly as wide as the round knuckles diameter. I thought that should be enough space to get some thin and flexible wires through the hinges to connect the electronics from the main body with the door.
Unmodified brass hinge 
Hinge screwed to the door 
Test fitting the hinge 
Here you can see the gap 
Loose test fitting 
Another view of the gap
I removed the pin with a hammer and a small flattened nail to separate the hinge parts. On the leave with two knuckles I carefully filed little dents to approximately half of the knuckle connection (this took a long time, filed by hand). On the leave with three knuckles I filed away a small part on the bottom side of the middle knuckle so that there was a small gap left to guide through the wires.
Removing the hinge's pin 
Hinge leaves and pin 
Filed little dents for the wires 
Another view of the dents 
New gap at the middle knuckle 
Wires will go through the gap
I splitted the long hinge pin and made two short pins that only go through one and a half knuckles. In the middle of the hinge the inner knuckle holes are used to guide through the wires.
Splitted and shortened pins 
Combined hinge leaves 
Combined hinge leaves 
Testing with a flexible wire 
Other side with flexible wire 
Test fitting the modified leave
After some test fittings I extended the hinge leaves for the main body by gluing on short 1 mm thick ABS stripes with ultra-strong 2-component epoxy. After letting it dry overnight, I drilled holes for M3 screws and shortened those screws. In my tests I was able to get four very thin and flexible, stranded copper wires through each hinge – that looked promising!
Test fitting the modified leave 
Wires will go throuth the middle 
That gap should be large enough 
Modified hinge with extensions 
Glued with ultra-strong epoxy 
Four wires fit through the hinge
The main body had thicker wall supports in the area of the hinges, probably to be thick enough to get the screws in that came with the kit. I removed these supports because I wanted to glue in nuts to be able to easily remove the hinges during the following building process.
The local hardware store only had M3 nuts and screws in stock, so I used them. The screw heads were quite large, but the height of the nuts was perfect for getting the hinges in the ideal position.
I secured the body with inserted hinges in a stable, upright position before applying the first small dots of epoxy glue to hold the hinges in place. After letting it dry completely overnight I carefully unscrewed the screws and removed the hinges. Then I applied a lot more of the ultra-strong epoxy around the nuts and let it dry overnight again.
Existing supports for the hinges 
Removed resin hinge support 
First fix with epoxy glue dots 
Added more epoxy to fix the nuts 
Customized hinges in place 
Notice the gap for the wires
