It comes up between the inner and outer skins, plenty of room between the two.
Its easier to work from the tub outwards and if you need to get anything through the other way drop a bit of rope through the hole, tape it to the wire then feed it back. That's how I did the second battery.
Its easier to work from the tub outwards and if you need to get anything through the other way drop a bit of rope through the hole, tape it to the wire then feed it back. That's how I did the second battery.