I have done a conversion but the method I've used would be to complicated to copy.
my ICE 2 has 2 motors (2 motorcars) with 10 intermediate cars.
on each coupling I've superglued 6 contacts 2 on each side and 1 on top & bottom.
I had 1 decoder and all wires (6) had been extended through the whole train.
1st wire: red = 2nd pickupshoe (2nd motorcar)
2nd wire: orange: common wire.
3rd wire: light for 2nd motorcar (white)
4th wire: light for 2nd motorcar (red)
5th wire: Aux 1
6th wire Aux 2.
all cars had led's.
I'm reconstructing the wiring by adding a function decoder into the 2nd motorcar.
This will eliminate the red wires and wires for headlighting(reverse) (2nd motorcar).
having 10 intermediate cars there is also a function decoder in the bord car, this function decoder will be removed and used in the 2nd motor car.
The end result will be as follows:
1st wire: orange common
2nd wire: Aux 1
3rd wire: Aux 2
the interior lighting is seperated into 2 circuits.
the wires from motorcar I will supply lighting for 5 cars and the same with the motor car II.
Car 5 and 6 will have no electrical connection as it would interfere with each decoder.




regards.,
John