No need to dismantle the fusebox. I've managed to run the wire through a plastic cover just behind the junction box. You just need to remove the ventilator for the A/C (the one beneath the glovebox) and you will see this round,gray cover. I've made a small hole in it and fed the wire straight to the DME box. Someone has also done the coding you have mentioned,but the paddles still dont work. Do you remember if after coding have you performed gearbox flash?
THIS IS HOW I RAN THE WIRE FROM JBBF (inside the cabin) TO THE X6021 (in the engine bay):
When you remove the AC fan which is located beneath the glovebox you will see a gray cover that leads to engine bay. On the picture you can see I already drilled a tiny hole in there and put the blue stick in there just to mark the spot:
This is where it comes out in the engine bay (basically straight in the DME box):
I ran the wire through there:
And straight to the X6021 ( pin no 12):
Et voila!
Unfortunately the paddles still don't work!